Question

The resistance of a wire is 20 ohms. It is so stretched that the length becomes three times, then the new resistance of the wire will be

• A. 6.67 ohms
• B. 60.0 ohms
• C. 120 ohms
• D. 180.0 ohms

Answer 1

Answer: (D)

180.0 ohms

Answer 2

In case of stretching of wire $R \propto l^{2}$

$\Rightarrow$If length becomes 3 times so Resistance becomes 9 times i.e. $R' = 9 \times 20 = 180\Omega$