Question

A wire of resistance $R_1$ is drawn out so that its length is increased by twice of its original length The ratio of new resistance to original resistance is:

• A. $9: 1$
• B. $1: 9$
• C. $4: 1$
• D. $3: 1$

Answer 1

Answer: (A)

$9: 1$

Answer 2

From the given options the correct answer is option (A): 9:1
R1=$\rho \frac{L_1}{A_1}$
R2=$\rho$($\frac{3L_1}{\frac{A_1}{3}}$)
$\therefore$ $\frac{R_2}{R_1}=9$