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The electric resistance of a certain wir...

The electric resistance of a certain wire of iron is R . If its length and radius are both doubled, then

A

The resistance will be halved and the specific resistance will remain unchanged

B

The resistance will be halved and the specific resistance will be doubled

C

The resistance and the specific resistance, will both remain unchanged

D

The resistance will be doubled and the specific resistance will be halved

Text Solution

Verified by Experts

The correct Answer is:
A
Material same `rArr rho` unchanged
`R=(rhol)/A=(rhol)/(pia^2) rArr R prop l/a^2`
therefore `R' prop (2l)/((2a)^2)`
`rArr R'=R/2`
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