Question

The resistance of a hot tungsten filament is about 10 times the cold resistance , what will be the resistance of 100 W & 200 v lamp when not in use ????

Answer 1

Answer:

Explanation:

As we learnt in

if R=r -

P_{max}=\frac{E^{2}}{4r}

- wherein

Power delivered will be maximum

 

P = VI = \frac{V^{2}}{R}

R_{hot} = \frac{V^{2}}{P}= \frac{200\times 200}{100}= 400\Omega

R_{cold}=\frac{400}{10}

           = 40\Omega