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A brass disc and a carbon disc of same r...

A brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is [`alpha` is temperature coefficient of resistance & Neglect linear expansion]

A

`|(alpha_(C)rho_(C))/(alpha_(B)rho_(B))|`

B

`|(alpha_(C)rho_(B))/(alpha_(B)rho_(C))|`

C

`|(alpha_(B)rho_(C))/(alpha_(C)rho_(B))|`

D

`|(alpha_(B)rho_(B))/(alpha_(C)rho_(C))|`

Text Solution

Verified by Experts

The correct Answer is:
A
`DeltaR_(B)+DeltaR_(C)=0`
`R_(B)alpha_(B)Deltatheta+R_(C)alpha_(C)Delta theta=0`
`(rho_(B)t_(B)alpha_(B))/(A)+(rho_(C)t_(C)alpha_(C))/A=0 implies (t_(B))/(t_(C))=(rho_(C)alpha_(C))/(rho_(B)alpha_(B))`
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