1.

The resistance of a wire is R. When this wire is stretched so that its length becomes double, its cross-sectional area becomes half. What will be the resistance of this stretched wire?

Answer»

`R/2`
`R`
`2R`
`4R`

SOLUTION :Original resistance of the wire `R = rho . L/A`
Resistance of the STRETCHED wire `R.= rho. (l.)/(A.)`
But 1 = 2 an A ` = A/2`
`:. R.=rho (2l)/(A/2) = (4) rho 1/A =4R`


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