Question

7. A small bulb has a resistance of 2 when cold. It takes up a current of 0.4 a from a source of 4v and then starts glowing. Calculate (i) the resistance of the bulb when it is glowing and (ii) elaborate on the reason for the difference in resistance?

Answer 1

Answer:

When not connected to the source the resistance of the bulb is 1 Ω. So,

the current is, I = V/R=2/1=2A.

Now, when the bulb is glowing the temperature of its filament increases and hence its resistance also increases. So, the new resistance is, R =