The resistance of a wire is `R` ohm. If it is melted and stretched to `n` times its original length, its new resistance will be

Options

A. `nR`
B. `R/n`
C. `n^(2)R`
D. `(R)/(n^(2))`

Answer

C

Explanation

Thinking Process Volume of material reamins same in stretching.
As volume remains same ,`A_(1)l_(1)=A_(2)l_(2)`
Now,given `l_(2)=nl_(1)`
`therefore New area `A_(2)=(A_(1)l_(1))/(l_(2))=(A_(1))/(n)`
Resistance of wire after stretching
`=prop.(nl_(1))(A_(1)//n).n^(2)=n^(2).R" "[beforeR=((prop)(1_(1))/(a_(1))]`