What is the Resistance of the Light Bulb

Introduction to what is the resistance of light bulb

Thomas Edison invented light bulb. The light bulb invented by Edison has high vacuum, high resistance and economic source of light energy. The light bulb works on the heating effect of electricity. As an electric current pass through the filament of the light bulb, the filament gets heated so that it produces light energy. The glass bulb contains vacuum or any inert gas to prevent the oxidation of the red-hot filament. The light bulb is made in wide range of sizes and voltages ranging from 1.5 volt upto 500 Volt. The light bulb has a low manufacturing cost and work on both alternating current and direct current. The light bulb is used in household purposes, commercial purposes, table lamps, headlamps, flashlights and for decorative purposes. Some heat-based applications of light bulbs are as use in brooding boxes in poultry, heat lights for reptile tanks, infrared heating, and toy oven etc.

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Description for the resistance of light bulb


The resistance of light bulb is calculated  by using Ohm’s Law. First we prepare the arrangement of a bulb with a source of potential difference or a battery , a voltmeter, a ammeter, a voltage regulator and connecting wires. Now pass the current through the bulb with the help of the source of potential difference and measure the reading of voltmeter and ammeter. Change the potential difference by the voltage regulator and find the 4 readings of voltmeter and ammeter. Now for every reading find the ratio of V is to I, we get the resistance of the bulb. If we plot the graph between the potential difference and the current we get the straight line, shows that the resistance of the bulb remains constant at constant temperature. We can find the resistance of the bulb by using the wattage of the bulb, this is the maximum resistance of the bulb.

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Example Based on the resistance of the light bulb


An electric bulb has the wattage of 220 V – 100 W. Calculate the resistance of the bulb.

We know that the power P = V^2/R

So R = V^2/P = 220 × 220 / 100= 484 ohm.