Question

a wire of length 1 metre has a resistance of 1 Ohm . it is uniformly stretched so that its length is increased by 25% , then its resistance is increased by ___?

Answer 1

Dear Student ,
As we know that the length of an wire is directly proportional to the resistance of the wire so ,
$$\begin{gathered} \frac{R}{R\text{'}}=\frac{l}{l\text{'}}=\frac{1}{1·25} \\ \Rightarrow \frac{1}{R\text{'}}=\frac{1}{1·25} \\ \Rightarrow R\text{'}=1·25\Omega \end{gathered}$$
Regards