Question

The resistance of a wire is 10 ohm. The resistance of a wire whose length is twice and the radius is half, if it is made of same material is

• A. 20$\Omega$
• B. 5$\Omega$
• C. 80$\Omega$
• D. 40$\Omega$

Answer 1

The correct option is C 80$\Omega$

$R=\frac{\rho l}{A}=10$

$R^1=\frac{\rho \times 2L}{\frac{A}{4}}$

$=\frac{8\rho L}{A}$

$R^1=80\Omega$