Thursday, June 6, 2013

Incoherent Light Source

Introduction to Incoherent Light Source:

Incoherent light source is any source of light which emit light of several wavelengths or say emit light of several colors shown in the case of the sun which is a best example of incoherent light source. The incoherent light sources are emitting light not only with different wavelengths but it emits light with different frequency and different amplitude and the light waves are out of phase. Different amplitude implies that if one light, emitted by the source has higher intensity than that of the other or say the content of one particular light is greater in the source rather compare to the other component of lights. The phase difference between the different light and say different color implies that if one color is emit at a particular angle than it is not necessary that all other colors present in the light source should have the same angle.

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Comparison of Incoherent and Coherent Light Sources


In the coherent light sources any two sources are said to be coherent if they emit light waves of the same frequency and nearly same amplitude and are always in phase with each other. These all properties are not satisfied by an incoherent light source as discussed above.

The coherent light source always exists in pair whereas the incoherent light source exists in single.

The coherent light source can be made using a single incoherent light source but the incoherent light source is generally exists in the nature.

Most of the light sources exist in the general life are incoherent whereas the coherent light sources are made in laboratory under specific conditions.


Conclusion for Incoherent Sources of Light


As per the discussion, we see that, when we observe the interference pattern of a coherent light source it shows a series of dark and bright bands with equal width on the both sides of the central band which either dark or bright but in case of the incoherent light source the interference pattern show mostly the central band as bright and the bands appears on the both side of it might be colored or dark and bright but the width of the bands is not equal.

Stream Energy

Introduction to steam energy:

There are two types of energy in nature i.e. conventional and non-conventional sources. Conventional sources of energy includes those sources of energy which derived from fossil-fuels. It includes petroleum, natural gas, diesel, etc.  Non- conventional sources includes those sources which are gift of nature and available free of cost to us. Such as Hydro energy, solar energy, Wind energy, Thermal energy. Geo-thermal energy etc. One of them is "Stream energy".  Steam energy refers to the form of the energy which is derived from the motion of water or wind. When water/wind is allowed to move at certain pace, it acquires tremendous energy due to its motion i.e. kinetic energy. Mainly, it is Kinetic energy, be it is in water or wind, which causes it to do work.

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Cause of Stream energy


Energy in stream is stored in the form of heat and pressure. When water or wind molecule is flowing,  the electrons start to move at high speed. This moving molecule of water takes to the air because of its quickly moving electrons. This moving water molecule keeps away from other water/wind molecules. This distance gives rise to pressure. When this task of moving wind/water is performed at large scale, enormous amount of pressure is built. When this pressure is released, energy can be generated. This energy is known as Stream Energy. Is this topic Equation for Kinetic Energy hard for you? Watch out for my coming posts.


Uses of stream energy:


Stream energy has industrial, agricultural and house hold uses. Stream energy is used in industries for power generation. The transfer of energy from the steam to the object causes it to move. Stream energy produced is used to rotate the turbine, which in turns rotates shaft of the generator.  Thus, electricity is produced. However there are certain limitations regarding the uses of stream energy. It can be used only under certain conditions and at certain places where there is ample scope of its availability. The geographical location of the place is a varying factor for the use of stream energy.

Reflection Theory

Introduction to Reflection Theory:

When a beam of light is incident on a surface,a part of it is returned back into the same medium.The part of light which is returned back into the same medium is called the reflected light.Thus,

The return of light into the same medium after striking a surface is called reflection.

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Theory of Reflection:

Reflection of light is the process which enables us to see different objects around us. Luminous bodies are directly seen,but non-luminous objects are seen only because they reflect the light incident on them.The reflected light on entering into our eyes,make them visible.

Different surface reflect light to different extents.A highly polished and smooth surface,such as plane mirror,reflects almost the entire light falling on it.

A plane mirror is made by silvering one side of a plane.The surface which is silvered,is called the silvered surface,while the other surface of glass plate is called the reflecting surface from where light is reflected.

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Kinds of Reflection:


There are usually two kinds of reflection:

1)regular reflection and

2)irregular reflection.

1)Regular reflection:Regular reflection occurs when a beam of light falls on a smooth surface and polished surface,such as a plane mirror.A parallel beam of light is incident on a plane mirror,the reflected beam is also parallel and it is in a fixed direction.This is called the regular reflection.

2)Irregular reflection:Irregular reflection occurs when a beam of light falls on a rough surface such as walls of a room or page of a book etc.The walls of a room or page of a book may appear smooth ,but if it examined under a microscope,it appears quite uneven having many small projections. When light rays strike different  parts of a rough surface,the rays are reflected in many different directions and give rise to the diffused or irregular reflections.

Emission and Absorption Spectra

Spectra are mainly classified as emission and absorption spectra

Introduction to emission and absorption spectra:

Emission S[spectrum] :

It is the spectrum of light emitted by a substance. Emission spectra are of three different types

1) Continuous Spectrum : It is a spectrum that appears as an unbroken continuous band of colours from red at one end to violet at the other end. In such a spectrum we can not say where one colour ends and the other colour starts. A continuous spectrum is emitted when a solid or liquid is heated to very high temperatures. It is due to the thermal excitation of the molecules of the substance. Its examples are solar spectrum, carbon are spectrum, spectrum of light emitted by an incandescent bulb etc. Having problem with Units of Angular Momentum keep reading my upcoming posts, i will try to help you.

2) Band Spectrum : A spectrum in which different colours appear as bands separated by dark spaces is called band spectrum. Each band is sharply defined at one edge called head of teh band and fading off gradually at the other edge. When a band is observed by an instrument of high resolving power, it is found that each band consists of a large number of fine lines. The band spectrum is due to the excitation of the molecules of an element or a compound. Its examples are the spectra of CO2 , N2 obtained by filling the gas at low pressure in a discharge tube and passing electricity through it, the spectrum of the light emitted by Bunsen flame etc.

3) Line Spectrum : It is a spectrum of bright lines separated by dark spaces. The line spectrum is due to the excitation of the atoms of an element. A line spectrum is obtained when electrons excited to higher energy states make transition to lower energy states as explained by Bohr's theory of atomic structure. Some of the examples are the spectrum of the light emitted by hydrogen in a gaseous discharge tube, mercury  vapour lamp, sodium vapour lamp, the spectrum of the light  emitted by salt solutions of sodium, lithium, potassium, barium, calcium etc, placed in the non-luminous portion of Bunsen flame.

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Absorption spectra: emission and absorption spectra

When an absorbing substance is introduced between a source emitting continuous spectrum and a spectroscope it is found that some regions of the continuous spectrum are missing. This is due to absorption of light. Generally  absorption occurs whenever light passes through any transparent substance. In addition, certain substances strongly absorb light corresponding to certain parts of the spectrum which is called selective absorption.

Absorption spectrum : The spectrum of the light absorbed by a substance due to selective absorption is called absorption spectrum.  Absorption spectra are of two types.

1) Line Spectrum  :  When while light from an incandescent electric bulb is sent through a Bunsen flame fed with sodium salt, the transmitted light is found to be a continuous spectrum crossed by two close dark lines. These dark lines lie exactly in the same position as the emission lines of sodium and constitute the line absorption spectrum of  sodium vapour. Line absorption spectrum of an element is obtained when the temperature of  the source of light is higher than that of the atomic vapour through which it passes.

2) Band Spectrum : The absorption spectrum in the form of groups or bands of closely spaced lines is called band absorption spectrum. It is characteristic of molecular  gases and chemical compounds. In face molecular spectrum is better studied in absorption spectrum.

Law of Gravitational Attraction

The law of gravitational attraction was proposed by Sir Isaac Newton in order to understand planetary motion around the planets. In this article we shall discuss the statement of the law.

Introduction to Law of Gravitational Attraction

“Everybody in the universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to the square of distance between them”

Mathematically, we can state this as:

                        F = G Mm/r^2

Where F is the magnitude of the attracted force between two bodies of masses M and m, separated by a distance r.

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Law of Gravitational Attraction

For the gravitational force between an extended object (like the earth) and a point mass, is not directly applicable.  Each point marks in the extended object will exert a force on the given point mass and these force will not all be in the same direction. We have to add up these force vectorially  for all the point masses in the extended object to get the total force.  This is easily done using calculus.  For two special cases, a simple law results when you do that:

1. The force of attraction between a hollow spherical shell of uniform density and a point mass situated outside is just as if the entire mass of the shell is concentrated at the centre of the shell. Qualitatively can be understood as follows:

Gravitational forces caused by the various regions of the shell have component alone the line joining the point mass to the centre as well as along a direction perpendicular to this line.  The component  perpendicular  to this line cancel out when summing over all regions of the shell leaving only a resultant force along the line joining the point to the centre.

2. The force of attraction due to a hollow spherical shell of uniform density, on a point mass situated inside it is zero.  Qualitatively, we can again understand this result.  Various regions of the spherical shell attract the point mass it in various directions. These forces cancel each other completely.

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The Law of gravitational Attraction : Summary


The law of gravitation is strictly true for point masses.  If the bodies are far apart, i.e. the distance between them is much greater than their sizes, then to a good approximation one may take r in to be the distance between there centers of mass. The gravitational force is a conservative force.

Monday, June 3, 2013

Wind Generator

Introduction to wind generator:

Wind generator: It is a device used for generating electricity by using power of wind. Let us go into the details of generator and how electricity is generated.

Electric generator: The device used for converting mechanical energy into electrical energy is called electric generator. The mechanical energy can be in the form of wind power , hydro power , coal power , nuclear power etc.Please express your views of this topic Electric and Magnetic Fields by commenting on blog.


Components of electric generator:


Components of electric generator:-

(1)   Magnetic field

(2)   Armature Coil

(3)   Mover

(4)   Rotor

(5)   Slip Rings

(6)   Stators

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Wind generator :


Magnetic Field – It is supplied by coils placed in the generator which get feed of current from a source.

Armature coil – It consists of a large number of coils wounded together. It is the current carrying member of the generator and here voltage is produced.

Mover – It is the external source which moves the generator such as wind power, hydropower, coal power etc .

Rotor – The component, which rotates with in the generator, is called rotor.

It gets the driving power from the mover of the generator.

Slip Rings – These are the circular conducting parts of a generator and are used to transfer electric power to external agency.

Stators- The stationary parts of a generator are called stators.

A wind generator has a wind turbine attached to it. It acts as a propeller for the generator and it rotates the rotor. The rotating rotor changes electric flux linked with the armature coil. The change in flux linked with the armature coil produces electric voltage and thus electric current is  produced.

Some of Advantages of wing generator is that it produces clean energy , without any pollution and polluting wastes. More over is utilizes naturally produced wind power , which if untapped results in wastage of natural power.

Some of the disadvantages is that it need a lot of space for setting up windmills.

It can be concluded that new technological advancements are required for setting up wind generators in small area

Sunday, June 2, 2013

5 Renewable Resources

Introduction to 5 renewable resources:
The natural resources such as sunlight, rain,geothermal heat, wind, tides etc generates the energy that can be renewable. About 19% of the global final energy consumption will come from these renewable resources. In that 19%, about 13% of the total energy coming from the biomass that is through biological processes which are used mainly for the heating purpose and about 3.2% of total energy coming from hydro power electricity. New renewable resources are used now a days such as modern biomass, wind, small hydro, solar, geothermal and bio fuels. These resources contributes for about another 2.7% of the total energy and are growing very rapidly. About 18% of the total renewable energy that is used for the generation of the electricity. About 15% of the global electricity is coming from the hydro power electricity and about 3% from the new renewable resources.Please express your views of this topic Definition of Light Energy by commenting on blog.


Some renewable resources


Wind power: The wind turbines runs with the help of the wind. Modern wind turbines ranges from around 600 kW to 5 MW of rated power, turbines with rated output of 1.5MW to 3 MW which has became a commercial use. Areas where there are stronger winds and are constant such as high altitude areas and these areas are the preferred locations for the wind farms which generates the electricity by using the wind called as wind energy.

Hydro power: Energy that can be produced from water that is stored in dams is called hydroelectric energy. Water in the dams can be harnessed and then they are used to generate the electricity. Water is used for this purpose because water is about 800 times more denser than that of air. Even in a slow flowing stream of water we can generate the considerable amount of hydro electric energy.

Solar energy: Solar energy is the energy that is derived directly from the sun in the form of solar radiations coming from sun. Some of the solar products are solar cooking, solar hot water, day lighting, space cooling and heating through solar architecture.

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More renewable resources


Biomass: Biomass which is a plant material is a type of renewable energy source where the energy comes from the sun. Plants capture the sun's energy through the process of photosynthesis. When we burn plants, the plants release the energy which the plants contain.

Biofuel: Liquid biofuel is a bioalcohol such as bioethanol or an oil such as biodiesel. Of the world’s transport fuel about 1.8% is provided by biofuels.

Geothermal energy: Geothermal energy is the energy that is used for generating the electricity from the steam that is produced by the water present inside the earth. When that water gets heated up this energy is generated and we use this energy as geothermal energy.

Longitudinal Mechanical Waves

Introduction to longitudinal mechanical waves:
A mechanical wave is a periodic disturbance which can be produced only in a material medium and it transfers energy from one point to medium and it transfers energy from one point to another without there being a direct contact between the two points.

Longitudinal waves are one of the types of mechanical waves. If the particles of the medium forward and backward along the same direction in which the energy propagates then the wave is known as the longitudinal wave.

Sound waves in air and the waves produce in a spring when it is pushed and pulled are examples of the longitudinal waves.Having problem with Wave Theory of Light keep reading my upcoming posts, i will try to help you.


Description of longitudinal waves with example

Consider a gas or air enclosed in a cylinder. The vertical lines represent different layers of the air in undisturbed position when no energy is travelling through it. Now when a longitudinal wave is sent through the medium, the layers of the air begin to vibrate in the same direction as the direction of the propagation of energy. In doing so a certain number of neighboring layers are brought closer together. At these points the pressure increases and a compression is set up.

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Compressions and rarefactions in longitudinal waves


At fixed distances compressions the layers are moved apart. Here the pressure decreases and a rarefaction is set up. As the energy propagates the compressions change to rarefactions and vice verse and they are equal spaced. The distance between the centers of consecutive compressions or consecutive or consecutive rarefactions is the wave length of a longitudinal wave. All other definitions given for transverse waves are valid for longitudinal waves as well. The longitudinal waves consist of alternate compressions and rarefactions. The maximum displacement of a layer on either side of its mean position is the amplitude of the longitudinal wave. The number of complete vibrations of the layers of the air in one second represents the frequency of the wave.



Inner and Outer Planets

Introduction to inner and outer planets:

Solar system consists of eight planets and they are divided into two groups inner planets and outer planets. The first four planets closer to the sun are inner planets and they are mercury, Venus, earth and mars. Jupiter, Saturn, Uranus and Neptune are outer planets. Asteroid belt separates the inner and outer planets and this is the region where thousands of asteroids can be found. Both inner and outer planets are characterized by different features. Inner planets are called terrestrial planets  as they have a solid surface and are similar to earth. Inner planets are composed of heavy metals such as iron and nickel and have few or no moons.

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Inner planets


Mercury: It is one of the densest planets in the solar system.The smallest  planet, mercury has no moons and is comprised mostly of iron and nickel.

Venus: It is known for its brightness and it has a rocky surface which is similar to the moon, it is hidden by its thick yellow atmosphere. Venus has no moon similar like mercury.

Earth: Earth is the largest and densest of the inner planets and it is the only place in the universe where life is known to exist.

Mars: It is smaller than earth and Venus and it possesses an atmosphere of mostly carbon dioxide  and  its surface is peppered with vast volcanoes such as Olympus moons and rift valleys such as Valles marineris. Two tiny natural satellites are present in mars and they are Deimos  and Phobos.

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Outer planets


Jupiter: It is 2.5 times the mass of all the other planets put together. It is comprised with a large amount of hydrogen and helium. It has 63 known well satellites.

Saturn: It has several similarities with that of Jupiter and it is distinguished by its extensive ring system. The rings are made up of small ice and rock particles.

Uranus: It is the lightest of all the outer planets and it has a much colder core than the other gas giants and radiates very little heat into space.

Neptune: It is slightly smaller than Uranus and it is more massive and dense. It also radiates more internal heat but not as much as Jupiter or Saturn.

4 Forces of Physics

Introduction to 4 forces of physics:

The four forces of physics are also termed as the fundamental forces of physics and they are: Gravity, Electromagnetism, Weak Nuclear Force also known as Weak Interaction and Strong Nuclear Force also known as Strong Interaction. Discussed  below are the types of forces.


The 4 types of forces in Physics


Let us see the four types of forces in physics

Gravity:

Gravity is the first fundamental force and it has the maximum reach but minimum strength. It is a force that is attractive and helps to keep 2 bodies close to each other even in void. It is the force that binds the planets in their orbits around the sun and the moon in its orbit around the earth. It is this force that helps things to stay on the earth. If it would not have been there we would not have been walking on earth.

Electromagnetism:

It is the second force by virtue of which charged particles interact with each other. Electric and magnetic forces were considered different but it was proved that these are same. It is the force which is most prevalent and it affects things kept far away at a reasonable force.

Weak Interaction:

It is a force which is quite powerful and it aids in phenomena like beta decay. It has been combined with electromagnetism as a unique interaction called weak interaction. It is the force that acts on atomic nucleus scales.

Strong Interaction:

It is the strongest force and has been appropriately named the way it is. It binds together the protons and the neutrons together. It is strong enough to bind together repulsive forces also that are present in atoms amongst positive protons.

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Conclusion for the 4 types of forces in physics


We can conclude that, Scientists believe that these 4 forces of physics are just 4 different names but in reality they are a unified force, a single entity. They believe that these 4 forces are run by a single force which is waiting to be discovered. By these 4 forces of physics, how particles react with each other and are the fundamental forces as we have seen above.

Friday, May 31, 2013

What Makes up the Atmosphere

Introduction to makes up the atmosphere:

The atmosphere is the layer of gases, which surrounds the earth containing air mixed with the water vapor. In beginning, the earth was much bigger and much cooler with no atmosphere, but later as the earth, started contracting and it became smaller and warmer after the process of differentiation. During this phase gases like water vapor, hydrogen, helium, methane and ammonia were liberated which form the atmosphere. Gradually gases lighter than water like hydrogen and helium were formed. Free oxygen came into the atmosphere, with the evolution of autotrophs from heterotrophs. Here we discuss how the atmosphere of earth makes up.

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What makes up the atmosphere?


Atmosphere is composed of 78% nitrogen, 21% oxygen, 0.03% carbon dioxide and 0.07% of other gases. The percentage of water vapor in the atmosphere is variable. There are different layers in the atmosphere, let us know them:

Thermosphere: In this layer of the atmosphere, temperature increases until they approach 2000°F or 1090°C at noon. The air is even thinner at this altitude than it is in the upper atmosphere. In fact, there is practically a vacuum so that little heat can be conducted. It was once called the ionosphere because of ionization of molecules and atoms that occurs in this layer, mostly because of ultra violet, but also X rays and gamma rays. Ionization refers to the process whereby atoms are changed to ions through the removal or addition of electrons, giving them an electrical charge.

Mesosphere: Right below thermosphere lies Mesosphere. In this layer of the atmosphere, temperature tends to drop with the increase in the altitude.

Stratosphere: Just below Mesosphere lies Stratosphere. This is one of the main layers and the temperature here is stratified which means that the cool layers are below the warm ones.

Troposphere: This layer is the lowest one of all and contains maximum water vapour. This layer constitutes the most of atmosphere's mass which is upto 75%.

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Conclusion for the constituents of atmosphere:

From the above discussion, we can conclude that air is essential for the survival of life. Air contains nitrogen, oxygen, carbon dioxide, water vapor, argon, helium, methane, krypton, hydrogen, ozone, carbon mono oxide, sulphur dioxide, nitrous oxide, nitrogen dioxide, etc. Oxygen of the atmosphere is essential for photosynthesis. Nitrogen is also present in the atmosphere, which is taken by the some plants directly. Nitrogen is also used for the production of ammonia, which is used for making the fertilizers.

Photovoltaic Solar Cells

Introduction to photovoltaic solar cells

The first practical photovoltaic solar cell was made by selenium in 1954. This photovoltaic solar cell could convert only 1% of solar energy into electricity. Now these days, solar cells are usually produced from the semiconductor materials, such as silicon and gallium. Semiconductors are the materials, which do not allow to pass electricity at the normal conditions. The conductivity of the semiconductors increases appreciably if certain types of impurities are added. This addition of impurities is called doping.

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Photovoltaic Solar cell


A device, which converts sunlight directly into electricity, is called a solar cell. The semiconducting material to which a small quantity of a specific impurity is added is called doped semiconductor material. For example, when a small quantity of arsenic is added to ultrapure silicon, the silicon so obtained is termed as doped silicon. The conductivity of such semiconductor materials increases when light falls on them and a potential difference is developed between the two points in the semiconductor material. This cause a flow of a electric current. A single silicon solar cell of about 4 squared centimeter develops a potential difference of about 0.5 volt at 60 milliampere current. Due to this reason the solar cell is also called as photovoltaic cell. A single solar cell produces very small current at a small potential difference. So, in practice, we use a large number of solar cells connected together. This combination of a large number of solar cells is called a solar cell panel. A solar cell panel can provide stronger currents under high potential difference. Photovoltaic solar cells gained much importance in the last few decades due to the following reasons:

(i) The fossil fuels such as coal, petroleum etc are depleting very fastly, whereas the photovoltaic solar cells are renewable sources of energy.

(ii) Combustion of fossil fuels produce high air pollution and leads to green house effect whereas photovoltaic solar cells does not produce any type of pollution.

(iii) It is an energy source that is inexpensive.

(iv) These are used in remote areas very easily.

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Uses of Photovoltaic Solar Cells


(i) Photovoltaic solar cells are used in street lighting in rural areas.

(ii) Photovoltaic solar cells are used for operating water pumps for domestic and agricultural purposes.

(iii) Photovoltaic solar cells are used in satellites.

(iv) Photovoltaic solar cells are used to operate TV and other electrical appliances in our daily life.

Transformer Output Voltage

Introduction to transformer output voltage:

A transformer is a device, which can convert high alternating voltage into low alternating voltage and low alternating voltage into high alternating voltage. The transformer is based on the phenomenon of the mutual induction. If the transformer converts, the high alternating voltage into low alternating voltage it is called the step down transformer and if it converts the low alternating voltage into high alternating voltage it is called the step up transformer.I like to share this Formula of Density with you all through my article.


Construction of Transformer output voltage :


A simple transformer consists of the two coils called primary coil and the other is called the secondary coil. In one of the coil the number of turns of thick, insulated copper wire is less as compared to the other. If the primary coil has more number of turns it behaves like a step down transformer and if the secondary coil has more number of turns it behaves like a step up transformer. If the numbers of turns in the primary coil are Np and the number of turns in the secondary coil are Ns. Let the input voltage is Ep and the output voltage is Es. According to the energy conservation, we get

Ep / Np = Es / Ns = k ( K is called the transformation ratio)

Here we get the output voltage Ep = Es Np / Ns

If Ns < Np then the output voltage is more than the input voltage and the transformer is step up.

If Ns > Np then output voltage is less than input voltage and the transformer is step down.

As the voltage is stepped up or stepped down the current is also reduced or increased in the same ratio.

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Example for the transformer output voltage :


The ratio of the number of turns in the primary and the secondary coil of a step up transformer is 1: 200. It is connected to ac mains of 200 V. Calculate the voltage developed in the secondary coil.

Solution

Here, Np / Ns = 1 / 200, Ep = 200 V

Es / Ep = Ns / Np

Es / 200 = 200 / 1

Es = 40000 Volt.

Wave Model of Light

Introduction to wave model of light

Up to the middle of the 17th century, it was believed that light consisted of stream of corpuscles, emitting by the light source and travelled outwards from the source in straight lines. This theory is known as the Newton’s corpuscular theory. However, after 1827, the experiments of Young and Fresnel on interference, and the measurement of the velocity of light in liquids by the Foucault demonstrated phenomena, which could not be correctly explained by corpuscles theory but could be explained by the wave theory of light.


Huygens wave theory of light


In 1678, Huygens proposed the wave theory of light. According to this wave theory, light travels in the form of waves. These waves after emerging from the light source travel in all directions with the velocity of light. As the wave requires the medium to travel, Huygens imagined an all-pervading medium called aluminiferous ether. It was assumed that the hypothetical medium is weightless and can penetrate through matter. It has all properties necessary for the propagation of light waves. Hence, it was assumed that the density of ether is very small and the elasticity is very large. Light waves travel in such a hypothetical medium. When these waves fall upon the retina of the eye, they cause the sensation of sight. Huygens proposed the geometrical construction to explain the propagation of a wave front in the medium and determined the position of the wave front after any interval of time. They are known as the Huygen’s principle.



Conclusion of Huygeng’s wave theory of light


Every particle of the medium situated on the wave front acts as a new wave source from which the fresh waves originate. These waves are called the secondary wavelets.

The secondary wavelets travel in the medium in all directions with the speed of the original wave in the medium.

The envelope of the secondary wavelets in the forward direction at any instant gives the new wave front at that instant.

How Big Is The Sun

Introduction on the sun:

Astronomers categorize the sun as a "Yellow G2 Dwarf." It is an average, middle-aged star. Without it there would have been no life on earth though. The life on earth has arisen because of its just the right distance from the sun at just the right moment in sun’s life and in a way we are lucky to be here at the right moment in the eternity of existence of universe.Having problem with Definition of Buoyancy keep reading my upcoming posts, i will try to help you.

Like all stars hydrogen nuclei fuse together to form helium nuclei leading to a burst of energy, heating up and powering the Sun and this atomic reaction makes the Sun lose a tiny amount of its mass continuously. We need not feel concerned though, as there is enough fuel to last a billion years or more.

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Explanation to how big is the sun:


The sun is big, very big. It constitutes 99% of matter in the solar system – remaining 1% being taken up by the  planets, comets, asteroids and moons of the solar system. It is equivalent to 330,000 times the mass of our earth. The Sun is about 1,391,980 kilometres (864,938 miles) in diameter. It is difficult to imagine as one can never see anything similar at close quarters. Compare it to our planet Earth, which is just 12,756 kilometres (7,926 miles) wide or let us take the biggest planet in the solar system, Jupiter, which is just 142,600 kilometres (88,700 miles) wide.


We can now see that the Sun is huge, but it is interesting to know that it is tiny in comparison to many other stars. A star called Betelgeuse is 0.5 billion kilometres wide and about 500 times the size of the sun! Stars tend to become bigger as they get older. Our Sun is still young and only about 4.5 billion years old, which is nearly half way through its life. It too will become bigger as it gets older and perhaps "eat up" some of the inner planets, Mercury, Venus, and possibly Earth and Mars too. Life will surely cease to exist on our planet Earth when that happens.

Sunday, May 26, 2013

Van De Graaff Generator

Introduction to Van de Graaff generator:

Let us learn about the van de Graaff generator. Van de graaff generator produces a continuous supply of charge on a large metal dome when a rubber belt is driven by an electric motor or by hand which is show in the figure. For example pens and combs made of certain plastics become charged when rubbed on your sleeve and can then attract scraps of paper.

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Positive and Negative Charge:


When a strip of polythene is rubbed with a cloth it becomes c harged. If it is hung up ans another rubbed polythene strip is brought near, repulsion occurs. Attraction occurs when a rubbed strip of cellulose acetate approaches.

This shows there are two kinds of electric charge. That on cellulose acetate is taken as positive (+) and that on polythene is negative (-). The force between electric charges decreases as their separation increases.


Demonstrations:


Let us see the demonstration of Van de Graaff generator. In our figure a, sparks jump between the dome and the discharging sphere. Electrons flow round a complete path from the dome. In part b why does the ‘hair’ stand on end? In part c the ‘windmill’ revolves due to the reaction that arises from the ‘electric wind’ caused by the action at points effect, explained above for the lightning conductor.Is this topic Average Speed Formula hard for you? Watch out for my coming posts.



Action:

Let us see the action of Van de Graaff generator. Initially a positive charge is produced on the motor-driven Perspex roller due to it rubbing the belt. This induces a negative charge on the ‘comb’ of metal points P, in figure a, which are sprayed off by ‘action at points’ on to the outside of the belt and carried upwards. A positive charge is then induced in the comb of metal points Q and negative charge is repelled to the dome. This concept will clearly explained you to know about the Van de graaff generator.

Pendulum Gravity

Introduction to pendulum gravity:

Galileo achieve the experiment scheduled acceleration suitable to gravity. He illustrate that condition substance are dropped consequently because to fall freely from the similar height they achieve the plane of the earth at the same time supply the resistence obtainable by the air through this method is neglected. This demonstrate to while substance are dropped they occurrence consistent acceleration due to the gravitational magnetism of the earth towards its earth.Is this topic Gravitational Acceleration Formula hard for you? Watch out for my coming posts.


Gravity:


This uniform attraction qualified through an object towards center of the earth is recognized as acceleration due to gravity. It is represented by the g with is definite as the energy experienced through an object having unit mass.

The importance acceleration suitable to gravity varies from place to place, average value is 9.81ms-2. It has a maximum value at the poles and a minimum value at equator.

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Type of pendulum gravity:


Simple pendulum gravity:

A simple pendulum is serious object resembling a bob balanced at one end of an inextensible and weights string. The further end of the string is attached to a rigid support. The point at that the string is attached is identified as point of suspension. A small metallic spherical bob attached to a thread signify a simple pendulum.

that executes harmonic motion, time period is independent of amplitude. The time period of the pendulum,  T = 2p`sqrt((1)/(g))`

Where l is the length of the pendulum and g is the acceleration suitable to gravity. The length of the pendulum is measured from the position of deferment to the middle of spherical bob.

Drawback of simple pendulum gravity:

The bob of the simple pendulum is not a point object and the string is not a weights string. The string also has a moment of inertia about the suspension axis. The simple pendulum is not an ideal one.

The motion of the bob is not merely a translation one but it also rotates about the point of suspension.

Compound pendulum gravity:

A compound pendulum is rigid body capable of oscillating freely about a horizontal axis passing through it. A rigid body of any shape and internal structure capable of making oscillation about a horizontal axis constitutes a pendulum.

Thermometer Calibration

Introduction to thermometer calibration:

we have read that on touching an object,if heat flows from our hand to the object,the object appears cold to us,while if heat flows from object to our hand,the object is said to be hot.but this method of finding the temperature is not reliable and not scientific.For scientific purpose,we need an accurate measurement of temperature.The instrument used for measuring the temperature is called a THERMOMETER.

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There are several types of  thermometer such as liquid thermometer,platinum resistance thermometer ,thermocouple thermometer,constant  volume gas thermometer,vapour pressure thermometer,magnetic thermometer and radiation thermometer.The choice of thermometer depends on the range of temperature to be measured,the accuracy required and the physical conditions of the substance of which temperature is to be measured.

Important note:The substance used in a thermometer must have some characteristic property that changes with temperature.Such a property is called the thermometric property of the working substance.


About thermometer calibration


The calibration of a thermometer  involves fixing of two points on it-one lower fixed point and other upper(or higher) fixed point and then dividing the interval between the lower and upper fixed points into a convenient number of  equal parts.Each part is called a degree.The fixed points are chosen in such a way that they can easily be obtained.

Lower and higher(or upper) fixed points

The melting point of pure ice at one atmospheric pressure(ice point) is taken as the lower fixed point. The boiling point of pure water at one atmospheric pressure (the steam point) is taken as the higher(or upper) fixed point.

Dividing the interval between the two fixed points

The interval between the lower and upper fixed points is divided in a suitable number of equal parts depending upon the scale of  temperature.Each interval is called a degree.For the celcius(or centigrade) scale,the interval is divided in one hundred equal parts,and for the Fahrenheit scale, the interval is divided into 180 equal parts.

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Uses of thermometer


Thermometer is used

To measure the temperature of a liquid and

To measure the patient's body temperature.

Water Based Lubricant

Lubricant is a substance which is used to reduce the friction between two moving parts .After applying the lubricants the efficiency of machines increases.The  ability of lubricants to reduce the friction between the two moving objects is known as lubricity.There are some other methods by which friction can be reduced like using the Ball and bearings but using lubricants is the best option. Main use of lubricant is in the transports. All the vehicles uses lubricants for the proper functioning  and longevity of the engines.

Lubricants are of various types

1)Solid lubricants

2)Oil based lubricants

3)Organic lubricants

Lubricants are also divided into the personal lubricant category. Under this category various types of lubricants are there

Water based lubricants
Silicone based lubricants
Oil based lubricants
organic lubricants

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Ingredients of Water based Lubricants


Majority of the lubricants used are water based. These lubricants are mostly recommended by the doctors and the health care people. Water based lubricants are more efficient and do not damage our body and can be removed from the body very easily as compared to the oil based or other lubricants.

There are few ingredients in the water based lubricants. The knowledge of ingredients of water based lubricants can help to prevent any kind of reaction or damage. Ingredients are given below

Preservatives and antiseptics

Glycerin.

Extras: warming, scented, flavored.

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Advantages and disadvantages of Water based lubricants

Advantages:

1)It is safe and secure to use

2)It can be easily removed from the body

Disadvantages

1)The water content dries up fast and becomes very tacky

Friday, May 24, 2013

Doppler Effect Uses

Introduction to Doppler effect uses:

The  whistle of a fast moving rain appears to increase in pitch as it approaches a stationary observer and it appears to decrease as the train moves away from the observer. This apparent change in frequency  was first observed and explained by Doppler in 1845.

The phenomenon of the apparent change in the frequency of sound due to the relative motion between the source of sound and the observer is called Doppler effect.Understanding Kinematics Formulas is always challenging for me but thanks to all science help websites to help me out.

The apparent frequency due to Doppler effect for different cases is deduced and this is applied in the various uses of Doppler effect.

Lets discuss the various uses of Doppler effect:

(i) To measure the speed of an automobile

An electromagnetic wave is emitted by a source attached to a police care. The wave is reflected by a moving vehicle, which acts as a moving source. There is a shift in the frequency of the reflected wave. From the frequency shift using beats, the speeding vehicles are trapped by the police.


Doppler effect uses - Tracing a satellite


The frequency of radio waves emitted by a satellite decreases as the satellite passes away from the Earth. The frequency received by the Earth station, combines with a constant frequency generated in the station gives the beat frequency . Using this, a satellite is tracked.

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Doppler effect uses - RADAR and SONAR


RADAR means Radio detection and ranging.

A RADAR sends high frequency radio waves towards an aeroplane. The reflected waves are detected by the receiver of the radar station. The difference in frequency is used to determine the speed of an aeroplane.

SONAR means Sound navigation and ranging

Sound waves generated from a ship fitted with SONAR are transmitted in water towards an approaching submarine . The frequency of the reflected waves is measured and hence the speed of the submarine is calculated.

Wednesday, May 22, 2013

Dielectric Material

Introduction to dielectric material:

Dielectrics are insulating materials. In dielectrics all the electrons are bound to their parent molecules and there are no free charges. Even with normal voltage or thermal energy electrons are not released. Dielectrics are non metallic materials of high specific resistance and have negative temperature coefficient of resistance.


Dielectric Constant and electric polarization:


Dielectric Constant  ( `epsi`r ) :   The dielectric characteristics of a material are determined by the dielectric constant or relative permittivity      `epsi`r  of that material. It is the ratio between the permittivity of the medium and the permittivity of  free space .

i.e.,      `epsi_r`  =  `(epsi)/(epsi_0)`  .  Since it is the ratio of same quantity, `epsi_r`  has no unit. It is a measure of polarization in the dielectric material.

Electric Polarization :  Let us consider an atom placed inside an electric field. The centre of positive charge is displaced along the applied field direction. Thus a dipole is produced. When a dielectric material is placed inside an electric field such dipoles are created in all the atoms inside. This process of producing electric dipoles which are oriented along the field direction is called polarization in dielectrics.


Important applications of dielectric materials:


Dielectrics are very widely used as insulating materials.

1. Electrical conductors made of Aluminium Copper which are used for electric wiring are insulated with a  outer jacket of plastic or rubber.

2. In heater coils ceramic bead are used to avoid short circuiting as well as to insulate the outer body from electric current.

3. In electric iron, mica or asbestos insulation is provided to prevent the flow of electric current to the outer body of the iron.

4. In transformers as well as in motor and generator windings varnished cotton is used as insulator.

5. In electricity distribution lines, porcelain structures are used as insulators between points of different potential. In between aluminium or steel - cored aluminium conductors running through different distribution points, acts as insulator.

Electrostatic Charge

Introduction to Electrostatic Charge:

Electrostatic charges are of two kinds : positive charge, negative charge. These names were given by ‘Benjamin Franklin’ in 1750.  For example – If we rub a glass rod with silk, the rod becomes charged. Similarly, an ebonite rod on being rubbed with cat-skin becomes charged. But the electrostatic charges of these rods are of different types, the one which is developed I the glass rod on rubbing it with silk and the other which is developed in the ebonite rod on rubbing it with cat-skin. The first is called the ‘Positive charge’ and the second is called the ‘negative charge’. These charges are called as electrostatic charges because they don’t move in the material.

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Quantization of Electrostatic Charges


Millikan’s oil drop experiment, and many other experiments have shown that in nature electric charges are found to be made up of integral multiples of a smallest amount of charge. This smallest amount is 1.6 x 10^-19 coulomb. It is denoted by ‘e’, and is charge of an electron. All existing charges are found to be ‘ne’ (where n is a positive or negative integer) such as   e, 2e, 3e, ……, -e, -2e, -3e,……… No charge is found in the fraction of e ( as 0.7e or 2.5e). it means that electric charges can’t be divided indefinitely.

This property of charge is called as ‘quantization’ or ‘atomicity’ of charge. Since e is the smallest unit of charge, it is called as ‘elementary charge’.

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Law of Electrostatic Charges


As per law of electrostatic charges ‘ Like charges  repel each other while unlike charges attract each other’. The force of repulsion or attraction between two like or unlike charges is called as ‘ Coulombian force’.   For example-  a positive charge will attract another negative charge while repel another positive charge. Similarly a negative charge will attract another positive charge while repel another negative charge.

Displacement Vector

Introduction to displacement vector
Vectors are the physical quantities which can be completely described by their magnitudes and as well as their directions. Without direction, there are no meaning of vector quantities. Suppose we are saying that you have to go 5 m and find a red flag so it is not sure whether we get the flag or not because we don’t know in which direction we have to move to find the flag. Therefore, displacement is a vector quantity. There are so many vector quantities in the physical world such as velocity, force, momentum, impulse, thrust etc.

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Displacement vector


Displacement vector is defined as the change in the position of the body in a particular fixed direction. Displacement vector is given by a vector drawn from initial position to the final position of the body. Displacement vector can be positive, negative or zero. The Standard Unit of displacement vector is metre and the other units are centimetre and millimetre etc. The magnitude of the displacement vector is less than or equal to the actual distance travelled by the object in the given interval of time. Displacement vector is the shortest path between two points and the direction displacement vector is always from the initial point to the final point.

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Characteristics of displacement vector


The main characteristics of the displacement vector are as follows:

(i) Displacement vector has the unit of length.

(ii) The displacement vector of a body can be positive, negative or zero. If a body moves towards right in the particular time interval, its displacement vector is positive. If a body moves towards left in any particular time, its displacement vector is negative. If a body completes one round around any closed path, its displacement vector is zero.

(iii) The displacement vector is not depends on the choice of origin of the position coordinates.

(iv) The actual distance travelled by a body in a given interval of time is greater than or equal to the magnitude of the displacement.

(v) The displacement of a body between two points is the unique path that takes the body from its initial to final position.

(vi) The displacement of the body between two positions does not give nay information regarding the shape of the actual path followed by the body between these two positions.

Wind Electric Generator

Introduction to wind electric generator:

Electricity is an essential part of our life.We can not even think of world without electricity in future.Electricity is required in each and every aspect of life .A country can not progress even a bit without power.To fulfill the meed of power so many power plants are made which generates good amount of electric power.There are many ways through which electricity is generated.Please express your views of this topic Energy Types by commenting on blog.

Thermal power plants

Hydro Power plants

Nuclear power plants

Geothermal power plants

These are the few methods by which power is generated.In thermal power plants some fuels like coal etc are needed which is used to heat water and thus steam generated is used ti rotate the turbine.and then the power is generated.similarly in hydro power plants water is used to rotate the turbine.In the nuclear power plant fission of radioactive element liberates large amount of energy which is used to produce the steam by heating of water and this is used to rotate the turbine and then power is generated.

Apart from these scientists have evolved a new method to generate power from the wind.A fast moving air is known as wind .so in this method wind is used ti rotate the turbine and hence it helps in the production of electric power.Wind turbine takes the energy from the wind and then it converts the mechanical energy into electrical energy.


Different parts of wind Mill


The turbine used in the wind mill mainly contains three blades.These are fast rotating blades whi8ch can rotate up to more than 300km per hour.The blades are of the length about 30 to 40 meters.And the pole is of the height 60 yo 90 meters.A gear box is also used which helps to step up  the generator.Some times the same speed generator is used but more power can be generated by the variable speed generator.The blades are made in such a way that it is not affected by the climate change.

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Advantages and Disadvantages of wind electric generator


Advantages:

It does not cause any pollution

Height of pole helps the to get high wind most of the time.

movement of Blade is always perpendicular to the wind  so it helps to attain maximum efficiency.

Wind is a natural resource so it can be used for ever unlike coal and radioactive elements which will last for ever.

Disadvantages:

The height of towers are so long therefore there is always a problem for transportation.

Installation is not easy.

Flow of wind is not consistent in some areas.So when there is no wind efficiency can decline.

Complete dependency on the flow of wind for the power generation

Thursday, May 16, 2013

Environmental Consequences

Introduction to environmental consequences:

Corn kernels are protecting the University of Missouri farmer Tim Reinbott $1,000 to $2,000 per annual year in utility cost, and are removing the need for propane to keep one of his greenhouses warm and which avoids the environmental consequences. Fifty-gallons of rainwater barrels save them all nighttime heating costs for another greenhouse. Which supports many tropical plants and wooden pallets that would otherwise be discarded are utilized to heat the farm's administrative center, again protects thousands of dollars in fuel costs. Is this topic Formula for Density hard for you? Watch out for my coming posts.


Small-scale farmers benefits of environmental consequences:


Small-scale farmers be benefited, too
The matter of the research is never to target just the commercial farmer the NU press release quotes Reinbott saying, “With the comprehensive strategies our utilization can be done on a small or large scale. We want the owners to be able to take what we have done and use it in their backyards.”

And those just doesn’t just talk: the headquarters  offered free workshops this month for livestock owners and native plant enthusiasts in the locality.

These are many part of the University's experimental farm project, the Bradford Research and Extension Center, where Reinbott works as superintendent and serves to avoid the environmental consequences.

The corn kernels are burned for the fuel in a different burner, as are the wooded pallets, and the water barrels are situated along with the back wall of the greenhouse to gain the sun’s rays, even in the winter. The water gains the heat by the sun during the daytime and then at night, discharges that heat into the greenhouse enough to keep the inner temperature from the winter.

Reinbott, who also fixed underground pipes that can be used to geothermal heat to keep the temperature of the greenhouse stabilized, estimates that these projects combines together and saves Bradford Farm about $13,000 in propane costs every year.

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Advantages of environmentally unfriendly fuels:


Reinbott trusts that farmers take the advantage of green technology that can be used for the marketing advantage: “Production of food while sustaining the environment will happen to be increasingly more important,” Reinbott said. “Being ‘pest free’ its not that different than heating greenhouses with corn or other raw materials. You’re using natural products to replace environmentally unfriendly fuels, to avoid environmental consequences.

Wednesday, May 15, 2013

Amplitude Modulation

Communication Systems are the systems used to transfer quality information from one point to another through various components. A technique called modulation is most common in communication systems for telecommunications. I like to share this Electric Circuit Simulator with you all through my article.

This is done by a component called modulator and is present at transmitter’s end. Opposite working component of the same is demodulator which is present at receiver’s end and performs reverse of the same.
It is a method or technique of changing a property of high frequency carrier wave in accordance to the modulating signal. Any of the one of the following properties is changed: amplitude, frequency and phase of the carrier wave. So, it is used to transfer an information signal (modulating signal) inside another signal (carrier wave).

Amplitude form of adding information signal is a technique of varying amplitude of the carrier wave according to the instantaneous amplitude of the modulating signal. For example if the instantaneous amplitude of modulating signal is positive then the amplitude of carrier wave will be increased while if the amplitude of modulating signal is negative then the amplitude of the carrier wave will be decreased.
advantages of amplitude modulation is that long distance propagation is possible through it. Also amplitude form is cheaper and less complex. The coverage area of AM receivers is large.
Let us understand what is frequency modulation now: This is another technique of analog modulation in which instantaneous frequency of carrier wave is varied according to the instantaneous values of modulating signal (which carries information).  This technique is mostly used in music and voice broadcasting, radio systems, video transmissions etc.

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digital frequency modulation is a technique used for transmission of digital signal or digital stream . This is done by shifting the frequency of carrier wave among a range through a technique called frequency shift keying. The digital information is transferred by discrete frequency changes in carrier. The simplest technique of frequency shift keying is binary shift keying. In this technique binary information is transferred using a couple of discrete frequency. Binary information is in the form of 0 and 1. Here 1 is called mark frequency and 0 is called space information.

pulse width modulation definition : it is a technique of changing the digital signal into pulses to simulate a change in voltage. Terms used in PWM: period: time taken to complete pulse cycle. Frequency: number of pulses generated in a unit time and duty cycle: time in a period for which pulses are high. The technique uses rectangular pulses whose width is modulated such that average value of waveform varies.

Wavelength Example

Wavelength can be defined as the distance between the two consecutive shapes that are similar for a wave. That is for a repeating shape in the wave structure if we consider the distance between it and its first occurrence or between any two consecutive occurrences of it then the distance can be called as the wavelength. Please express your views of this topic Frequency to Wavelength by commenting on blog.

Now the next obvious question is what those shapes are or what shapes should be considered valid? For example let us consider Crests or troughs of the wave as the shapes. So the distance between two consecutive crests or any two consecutive troughs will be called as wave length.
The Symbol of the same is lambda. It is denoted by an inverted V with a head. (?). The symbol is Greek. The unit used in MKS system is meter. The distance is what we are referring here and hence the unit.
Let us talk about Wave-length Formula now. As we know that wave speed = Wavelength / period = lambda / T so Wave-length. = Wave speed * Period.

Here wave velocity (with direction) has been simplified and only its magnitude (wave speed) is considered.
What is Wave length? The answer to this question can vary with the type of the waves. But the basic formula remains the same. For some wave the speed always remains constant, however the frequency can vary when they move from one medium to another.

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Formula for Wave length can also be found in the equation of wave speed. . It is the relation between the frequency of the wave and its wavelength. The speed of the wave will be expressed in meter per second. That Is in MKS system. As far as the equation is considered we have frequency expressed in Hertz and wavelength expressed in meter.

Also Lambda = 2 pi / k where k is the wave number.
We can also say that k = 2 pi / lambda = 2 pi F / v ( v = wave speed) = omega / v
Or lambda = 2 pi / k = 2 pi v / omega = v / f. This is the basic derivation for the wavelength formula.
We also have a general representation of wave wherein we can see wave length as the variable.
Y (x, t) = A cos ( 2 pi (x / lambda – ft ) ) = A cos ( 2 pi / lambda ( x – v t )
Here v = wave speed
Lambda = w. l
F = frequency
T = time period
Pi = 3.14

Thursday, May 2, 2013

Geothermal Wind Energy

Introduction about Geothermal Wind Energy:

Let us see the introduction about Geothermal Wind Energy. Geothermal energy is used to store the heat in the earth and it extracted the power from earth. The motion of the wind is converted into mechanical energy by rotating the wind turbine also called wind mill, which is used to produce electricity. Let us see the theory for Geothermal Wind Energy.

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Theory for Geothermal Wind Energy:


Geothermal Energy:

The range of geothermal energy resources around the hot water and hot rock is found the surface of the earth. The heat exchanger of a geothermal energy system of pipes is buried to the ground. The geothermal energy is generated by the production of electricity from the heat.

Wind Energy:

Wind is caused due to absorption of solar energy on the earth surface and the rotation of the earth. Wind mills are used to extract energy from the wind and to produce mechanical work. Due to this alternate heating and cooling occurs and air movement is caused as there is pressure difference.

Generator:

The shaft of the gear box is coupled to a generator. The mechanical work of the rotor is converted into electrical power by the generator.

Wind mill:

Rotor is the most important component of the wind power plant.

Let us see the advantages and disadvantages of geothermal wind energy.

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Advantages and Disadvantages of Geothermal Wind Energy:


Advantages of Geothermal Wind Energy:

Geothermal energy is used for the home appliances and heat is taken from the earth.
Wind energy is freely available and inexhaustible.
Geothermal wind energy power production cost is low.
No consumption of fuel and hence no fuel cost and transportation problems.
Disadvantages of Geothermal Wind Energy:

Wind energy is not continuously available and fluctuating in nature.
Noisy in operation.
Large land area is required.
These are advantages and disadvantages of geothermal wind energy.

Respiration in Human Beings

Introduction to respiration in human beings

Respiration is the process by which diffusion of gases occur. Humans need continuous supply of oxygen for cellular respiration and need to get rid of excess carbon dioxide. Lungs are the organs of respiration in human beings and are composed of millions of tiny air sacs clustered as grapes known as alveoli.

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organs of respiration in the human beings


Nostrils-helps in breathing
Nasal cavity
Pharynx
Glottis (vocal cords)
Larynx (voice box)
Trachea (windpipe)
Bronchi-Trachea bifurcates into left and right bronchi, which enters each lung and divides further into bronchioles. Bronchioles deliver the air into alveoli.
Lungs- Lungs of human beings are packed with numerous tiny sacs called alveoli, which provide huge surface are for gaseous exchange. Air enters these structures through the system of air passages.

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Mechanism of respiration in human beings


Breathing is the mechanism by which gas is from the atmosphere enters into the human body. It divisible into two phases namely, inspiration and expiration. During inspiration, air always flows from a region of high pressure (atmosphere) to a region of lower pressure and during expiration the air from the lungs are expelled out.

Breathing is done through nostril and from nostrils the airs pass through nasal passages, pharynx, larynx, trachea, main bronchi, smaller bronchial tubules, bronchioles, and finally into a microscopic air sac called an alveolus.

The alveoli are surrounded by extensive network of blood vessels called capillaries. The exchange of oxygen in air for carbon dioxide in the blood occurs across the walls of alveolus of lungs.

This oxygenated or oxygen enriched blood then flows out through capillaries and feeds oxygen for the cells through circulatory system.

Cells present in the body tissues needs oxygen for cellular respiration and need to get rid of the carbon dioxide, so the blood is carried throughout the body exchanges oxygen and carbon dioxide with the body's tissues.

Wednesday, May 1, 2013

Thermoelectric Thermometer

Introduction to thermoelectric thermometer:

A thermometer is used to measure temperature  of a body. Temperature may be defined as a thermal condition of a body which determines its ability to transfer heat to other bodies. The thermal equilibrium of two bodies  kept in contact for a ling time can be tested by a third body which is a device used to measure temperature. Such a device is called thermometer. A device which measures the thermal condition of a body i scaled thermometer.

Thermometers are classified depending upon the physical property of substance  used  in them such as Liquid thermometers , Gas thermometers, Resistance thermometers , Thermoelectric thermometers, Radiation thermometers, Va pour pressure thermometers.

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Thermoelectric thermometer


When the junctions of two dissimilar metals are maintained at different temperatures an emf is generated. This effect is called thermoelectric effect or Seebeck effect. The pair of metals used to generate the emf  is referred to as a thermocouple. The emf causes a current in the circuit as shown by the deflection produced in a galvanometer  introduced in the circuit as shown in the figure below.

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The emf increases with the temperature difference between teh hot and cold junctions of a thermocouple. It reaches a maximum value at a certain temperature of thehot junction called neutral temperature.

Thermoelectric thermometer is based on the thermoelectric effect. Keeping the cold junction in melting ice and heating the hot junction to different temperatures determined by a constant volume hydrogen thermometer, the emf at each temperature is measured. A calibration curve is drawn plotting emf against temperature. Then the temperature of any body can be found from the graph by measuring the emf, keeping the body in contact with the hot junction.

Thermocouples are used to measure temperatures in the range of -250^0 C to 3000^0 C.

Magnetic Field Generator

Magnets or magnetized and unmagnetized pieces of iron are constituted of molecules that themselves have magnetic character. Each elementary magnet possesses a north pole and a south pole.

The reason why an unmagnetized piece of iron does not exhibit magnetic properties or doesn’t generate magnetic field is that different molecular magnets form pole of one of the molecular magnets on a neighboring molecular magnet is exactly counterbalanced by the opposite pole of the other molecular magnet situated much closed to it for magnetic field. Please express your views of this topic Dipole Magnetic Field by commenting on blog.

The process of magnetization or generating magnetic field does not create any magnetism in the magnetized body but rearranges the molecular magnets. As a magnet is rubbed along an iron bar the molecular magnets are forced to break up their closed groups, lose magnetic field and tend to arrange themselves in an end to end sequence so that the north pole of every molecular magnet is situated close to the south pole of another molecular magnet.


How magnetic field is generated


At every stroke of the magnetizing magnet greater and greater number of molecular magnets arranges themselves in continuous chain along the direction of the stroke. Ultimately a stage is reached when all molecular magnets get arranged in row parallel to the magnet with the same free pole of the molecular magnets situated at same end of each row. All these free molecular polarities situated at each extremity of the magnetized piece North Pole at one end and the South Pole at the other.


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Soft iron can be easily magnetized even by a weak magnetic field, whereas steel can be magnetized only by a strong magnetic field. Therefore, less energy is required for magnetizing soft iron. Soft iron loses its magnetism immediately, whereas steel retains its magnetism.

It is observed that if a magnet is subjected to rough treatment such as dropping from a height or hammering then it gradually loses part or whole of its magnetism.

Thursday, April 25, 2013

Law of Equipartition of Energy

Equipartition of Energy

The theorem of equipartition of energy states that molecules in thermal equilibrium have the same average energy associated with each independent degree of freedom of their motion and that the energy is serves well in the definition of kinetic temperature since that involves just the translational degrees of freedom, but it fails to predict the specific heats of polyatomic gases because the increase in internal energy associated with heating such gases adds energy to rotational and perhaps vibrational degrees of freedom. Each vibrational mode will get kT/2 for kinetic energy and kT/2 for potential energy - equality of kinetic and potential energy is addressed in the virial theorem. Equipartition of energy also has implication for electromagnetic radiation when it is in equilibrium with matter, each mode of radiation having kT of energy in the Rayleigh-Jeans law.

For the translational degrees of freedom only, equipartition can be shown to follow from the Boltzmann distribution.

Thermal Energy

The average translational kinetic energy possessed by free particles given by equipartition of energy is sometimes called the thermal energy per particle. It is useful in making judgements about whether the internal energy possessed by a system of particles will be sufficient to cause other phenomena. It is also useful for comparisons of other types of energy possessed by a particle to that which it possesses simply as a result of its temperature.

The calculated thermal energy provides a useful comparison for the energies involved in other physical phenomena. For example, in the interaction of radiation with matter it is useful to compare the quantum energy of the photons of the radiation with the thermal energy at the existing temperature. The photon energy associated with the photons in a microwave oven at frequency 2.45 GHz is about 10-5 eV. The average thermal energy at 20°C is 0.04 eV, about 3700 times higher. This suggests that the specific effects of the microwave photons in rotating molecules will be quickly randomized by the overwhelming thermal energy of the surroundings, so that the contribution of the microwaves will be "thermalized" or appear as a contribution to raising the temperature of the material.

Internal Energy for Ideal Gas

Internal energy in general includes both kinetic energy and potential energy associated with the molecular motion. But the potential energy is associated with intermolecular forces and is presumed to be zero in an ideal gas where the only molecular interactions are the perfectly elastic collisions between molecules. Therefore the internal energy of an ideal gas is entirely kinetic energy.

Internal Resistance Circuit

Introduction to internal resistance circuit

The internal resistance is due to the cell or battery in the circuit. The internal resistance of a cell is due to the electrolyte between the two electrodes. Ant current in the battery must flow through the internal resistance. The internal resistance acts in series combination in the cell. There is a voltage drop during charging and discharging the cell.

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Internal resistance circuit


When we connect the plates or the electrodes of the cell by a wire so that the circuit is completed, the current flows outside the cell from the positive electrode to the negative electrode of the cell. The direction of flow of current inside the electrolyte is from negative terminal to the positive terminal of the cell. So that the resistance offered by the electrolyte of the cell is known as to be the internal resistance of the cell. Because of the internal resistance of the cell a part of the energy given by the cell is lost in the form of heat inside the cell itself. The internal resistance of the cell is not a constant quantity, it increases slowly as the cell used. The internal resistance of the circuit is denoted by r and it is always in the series combination with the cell used. In the case of discharging of a cell, let E be the emf of the cell, V be the terminal potential difference across the cell and r be the internal resistance then

r = (E/V – 1) R

where, R be the external load resistance of the circuit.

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Factors on which the internal resistance of the circuit depends


The internal resistance of the cell depends upon the following factors:

(i) The internal resistance of the cell is directly proportional to the separation between the plates.

(ii) The internal resistance of the cell is directly proportional to the area of the electrodes dipped in the electrolyte solution.

(iii) The internal resistance of the cell depends on the nature, concentration and the temperature of the electrolyte of the cell. As the concentration and the temperature of the electrolyte increases the internal resistance also increases.

Radiation Shielding

Radiation protection, sometimes known as radiological protection, is the science of protecting people and the environment from the harmful effects of ionizing radiation, which includes bothparticle radiation and high energy electromagnetic radiation.

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Ionizing radiation is widely used in industry and medicine, but presents a significant health hazard. It causes microscopic damage to living tissue, resulting in skin burns and at high exposures and statistically elevated risks of disesesat low exposures.

Radiation protection can be divided into occupational radiation protection, which is the protection of workers; medical radiation protection, which is the protection of patients; and public radiation protection, which is protection of individual members of the public, and of the population as a whole. The types of exposure, as well as government regulations and legal exposure limits are different for each of these groups, so they must be considered separately.

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Radiation Shielding


There are three factors that control the amount, or dose, of radiation received from a source. Radiation exposure can be managed by a combination of these factors:

1.    Time: Reducing the time of an exposure reduces the effective dose proportionally. An example of reducing radiation doses by reducing the time of exposures might be improving operator training to reduce the time they take to handle a source.

2.    Distance: Increasing distance reduces dose due to the inverse square law. Distance can be as simple as handling a source with forceps rather than fingers.

3.    Shielding: The term 'biological shield' refers to a mass of absorbing material placed around a reactor, or other radioactive source, to reduce the radiation to a level safe for humans.[1] The effectiveness of a material as a biological shield is related to its cross-section for scattering and absorption, and to a first approximation is proportional to the total mass of material per unit area interposed along the line of sight between the radiation source and the region to be protected. Hence, shielding strength or "thickness" is conventionally measured in units of g/cm2. The radiation that manages to get through falls exponentially with the thickness of the shield. In x-ray facilities, the plaster on the rooms with the x-ray generator contains barium sulfate and the operators stay behind a leaded glass screen and wear lead aprons. Almost any material can act as a shield from gamma or x-rays if used in sufficient amounts.

Simple Machines Work

Introduction to simple machines work:
Ancient people invented simple machines to do their work easily against different kinds of opposing forces.In the 3rd BC.the Greek philosopher Archimedes, studied the simple machines like lever, pulley, and screw.A mechanical device that alters the magnitude/direction of a force is called as a simple machine. A combination of these simple machines can form complex machines.

Work: Exertion of a force to overcome resistance.

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Principles of simple machines


A simple machine works on the principle of a lever.

A lever is a rigid, straight or curved bar, which rotates around a fixed point called the fulcrum. It has an effort/applied force and a load/resistant force.

First lever: The fulcrum is between the effort and load.
Scissors, Crowbars, pliers and seesaws.

Second lever: The resistance force is between the fulcrum and the effort force.
Wheel barrows, Nut crackers and bottle openers.

Third lever: The effort is between the fulcrum and the load.
Hammers, Tweezers and shovels.


Work of simple machines


A machine by the following functions makes work easier:

Transfer of force

The direction of a force is altered

The magnitude of a force is increased

The distance/speed of a force is increased.

Simple machines are of six types, such as the wheel and axle, lever, the inclined plane, the pulley, screw and the wedge.The ratio of output divided by input is called as Mechanical advantage.

Mechanical Advantage = output/input

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Conclusion to simple machine work


From the discussion made above, we can conclude that, the work done by the effort is equal to the work done on the load.

Work = Force x Displacement

Unit of work is a joule

Wednesday, April 17, 2013

Types of Waves

Standing Waves on a String Lab

Let’s think about a string that is tied to a wall from one end and is being pulled in opposite direction from other end. Now suppose that it is being vibrated with a particular frequency.
The vibration will produce a wave that will pass through the length of string and will reach at its distant end that is tied with wall.

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Now as the wave hits the wall, it will be reflected and will travel through the string in opposite direction. As we know that for every action, there is equal and opposite reaction. Result of wave hitting the wall will be refection of wave in opposite direction. If the incoming wave has positive amplitude, the reflected wave will have negative amplitude.

Now suppose that second incident wave enter the string and travel through its length with positive amplitude. The reflected wave with negative amplitude will interfere with incident wave with positive amplitude at a particular point of string. If we provide many incident pattern of forms one after other, they will be interfered by the reflected ones.
Since both the forms have opposite amplitude, the standing pattern will be generated, hence the name.

Examples of Standing Waves

Standing forms are unique in having nodes and internodes that are the region of zero and intense disturbance respectively.
These do not cause the particle to travel instead; they make the particles to vibrate up and down. If cord, cable or string is vibrated with harmonic frequency, standing forms are generated.
Examples include the forms travelling through guitar string or water in lake or river. Any two identical forms with particular frequency can also produce standing forms.

Elastic Waves

These are characterised by movement of particles due to disturbance followed by appearance of a force to restore their initial position.
The magnitude of force is proportional to the magnitude of displacement of medium particles. It can be best understood by taking example of gas.
Gas is a compressible form of matter that can be compressed to desired volume by applying external pressure. Removal of pressure resumes the initial positions of gas particles.
Now if we allow the sound forms to travel through gas, it will be an example of elastic.

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Standing Waves Definition

Standing forms are defined as something that is produced by reflection and interference of incident forms. Here the equal and opposite amplitude of reflected and incident forms cancel each other out, giving the appearance of the standing forms.

Examples of Surface Waves

These are seismic forms that travel near the earth surface. Example would be ocean surface patterns waves.

Radioactivity

Radioactivity

Radioactivity is a physical process that includes emitting of radiations from unstable atoms. These atoms achieve stability through the process of radioactive decay. A radioactive atom emits energy and particles during its decomposition which are referred to as radiations. Radioactive decay can be natural or induced. Natural radioactive decay includes natural decomposition of radioactive atoms. It is categorised into three categories namely alpha radiation, beta radiation and gamma radiation.

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Radioactive Waste

Radioactive waste includes waste materials produced during the process of radioactive decay. It is categorised into various groups on the basis of its level of harmfulness to people. Some of them are as following.
Exempt waste and very low level radioactive waste includes the waste that are least or even not harmful to people and surroundings. Low level radioactive waste is generated in hospitals and nuclear fuel cycle that contain very small amount of short living radioactive decay.
Intermediate level radioactive waste contain relatively higher amount of nuclear decay and should be managed to avoid its harmful effects. High level radioactive waste is produced in nuclear reactors and as the name suggests it has very high level of nuclear decay and is very harmful to people and environment if not managed properly.

What is Radioactivity

Radio-activity is feature of some unstable atomic nucleus that emits radiations spontaneously. These unstable nuclei do so in order to achieve a stable configuration. Hence they emit some energy in form of radiations. Ability of these nuclei to emit radiations spontaneously is referred to as nuclear decay. Say for example, an atomic nucleus has too many neutrons. These excess neutrons make this nucleus unstable.

Hence this nucleus emits a negatively charged beta particle and thereby converting one neutron into proton. Likewise an atom with excess protons emit positron and thereby converts one proton into neutron. Hence the atom gets rid of excess subatomic particles by emitting radiations. The whole process is referred to as nuclear decay.Is this topic Equation for Kinetic Energy hard for you? Watch out for my coming posts.

Radioactivity Definition

Nuclear decay is a physical process defined as ability of atoms to emit radiations spontaneously.

Who Discovered Radioactivity

H. Becquerel discovered radioactive decay during his studies on properties of X-rays. He demonstrated that atoms of Uranium have ability to emit radiations spontaneously without any external energy source.
Later M. Curie and her husband Pierre coined the term “radioactivity”. They showed that ore of Uranium had more radioactive decay than the pure Uranium. This was due to the presence of other radioactive elements in the ore namely polonium and radium.