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If a wire of resistance 25Omega is unifo...

If a wire of resistance `25Omega` is uniformly stretched until its length becomes three times its original length then its new resistance is

A

`1//8`

B

`1//6`

C

`1//10`

D

`1//4`

Text Solution

Verified by Experts

The correct Answer is:
A

Since, new Resistance = 4R
`4R = (rho(l-x))/A + (rho(x + 0.5l))/A^(.)`
where `A. = x/(0.5 l + x) A`
`therefore 4 xx (rho l)/A = (rho (l-x)/A) + (rho (x +0.5l)^(2))/(xA)`
`rArr 4l = xl + xl + 0.25l^(2)`
`rArr x/l = 1/4 xx 1/2 = 1/8 rArr 1/8 rArr x/l = 1/8`
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