Question

The resistance of hot filament of the bulb is about 10 times the cold resistance. What will be the resistance of 100 W-220 V lamp, when not in use? *

Answer 1

Explanation:

let hot resistance be R

let cold resistance be r

according to given conditions R=10r

given- power = 100w V=220v

P=vi

100=220×I

I=5/11

according to ohm's law

V=IR

220=5/11×R

R=484ohm

since when the lamp is not in use no current passes thus no resistance is created