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The resistance of hot tungsten filament ...

The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use?

A

`20 Omega`

B

` 40 Omega`

C

` 200 Omega`

D

` 400 Omega`

Text Solution

Verified by Experts

The correct Answer is:
B
(b) `P = Vi = V^2/R`
`R_(hot) = V^2/P = (200 xx 200)/100 = 400 Omega`
`R_(cold) = 400/10 = 40Omega`.
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