Question

A wire of length L and resistance R is streched to get the radius of cross-section halfed. What is new resistance

• A. 5 R
• B. 8 R
• C. 4 R
• D. 16 R

Answer 1

Answer: (D)

16 R

Answer 2

By using $\frac{R_{1}}{R_{2}} = \left( \frac{r_{2}}{r_{1}} \right)^{4}$⇒ $\frac{R}{R'} = \left( \frac{r/2}{r} \right)^{4}$ ⇒ $R' = 16R$