Question

a small bulb has a resistence of 2 ohm when cold . it takes up a current of 0.4 A from of 4 V and then starts glowing . calculate
1. the resistence of the bulb when it is glowing and
2. elaborate on the reason for the difference in resistence .

Answer 1

i) When the bulb glows:

V = I R —- Ohm’s law R = V/I = 4/0.4 =10 Ω

(ii) Resistance of the filament of the bulb increases with increase in temperature. Hence when it glows its resistances is greater than when it is cold.

i hope it will help you

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