A `10 Omega` thick wire is stretched so that its length becomes three times. Assuming that there is no change in its density on stretching, calculate the resistance of the stretched wire.

Explanation

Given `R_(1) = 10 Omega`
`l_(1) = l`
`l_(2) = 3l, R_(2)` ?

`R_(1) = (rho)/(V) l_(1)^(2)`
`R_(2) = (rho)/(V) l_(2)^(2)`
`(R_(2))/(R_(1)) = ((l_(2))/(l_(1)))^(2) implies (R_(2))/(10) = ((3l)/(l))^(2)`
`:. R_(2) = 10 xx 9 = 90 Omega`.