Question

A bulb when cold has 1 resistance. It draws a current of 0.3A when glowing from a source of 3V. Calculate the resistance of the bulb when flowing and explain the reason for the difference in resistance.

Answer 1

Explanation:

here current, I is 0.3A

resistance of filament (when cold), R is 1Ω

potential difference, V is 3V

resistance of filament (when glowing)

R= $\frac{V}{I}$

R= $\frac{3}{0.3}$

R=10Ω

the resistance of filament increase from 1Ω to 10Ω due to increase in temperature of filament. because most of electrical energy converted into heat and light energy so that's why resistance of glowing filament is high.

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