A small bulb has a resistance of 2 ohm when it is cold. It draws 0.4 ampere current from a source of 4 V and then starts glowing. Calculate the resistance when it is glowing.

Given: Resistance (R cold) = 2 Ohm

Current (I) = 0.4 Ampere

Voltage (V) = 4 V

The resistance when the bulb is glowing is calculated by using Ohm’s law.

According to Ohm’s law,

V = I x R

Substituting the values in the above equation, we get

R = 4/0.4

R = 10 Ohm


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