Question

 A small bulb has a resistance of 2Ω 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

using the formula R= V/I

where R is resistance V is voltage and I is current

R=4/0.4

R=10 ohms

(ohms is the unit of resistance use the symbol of ohms used in the question)

The resistance of the bulb is much less when it is not glowing because resistance is directly proportional to potential difference by current . if the bulb is not glowing it means that the current is not flowing and so it has very less potential difference . As the potential difference is less , the resistance is also less.

Answer 2

Answer:

10 ohms

Explanation:

I= V/R

R = 4/0.4

R=10 ohms

Reason for the difference in resistance : resistance will depend on temperature of the conductor. so there will be difference in the resistance when it is glowing.