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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
`P = Vi= (V^2)/( R)`
`R_("hot") = (V^2)/( P) = ( 200 xx 200 )/( 100 ) = 400 Omega`
`R_("cold") = ( 400)/( 10) = 40 Omega`
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