Question

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Board on Wednesday
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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
(ii) Elaborate on the reason for the difference in resistance?

Answer 1

Resistance of the bulb when glowing=2 ohms

current = 0.4 ampere

voltage= 4 volts

(i). resistance when glowing:

R=V/I

R= 4/0.4 = 10 ohms.

All the very best for your exam...

Answer 2

Here’s the answer

1.We know V/I=R

Given V=4V and I=0.4A

Therefore 4/0.4 =40/4

=10 ohm

2. Resistance increases with increase in temperature