Question

How does the resistance of a wire change when its radius is tripled?

• A. Resistance decreases 9times
• B. Resistance decreases 3 times
• C. Resistance will be 9times
• D. Resistance will be 3times

Answer 1

The correct option is A Resistance decreases 9times

Resistance of the wire $R=\rho \frac{L}{A}$ where $A=\pi r^2$

$⟹$ $R\propto \frac{1}{r^2}$ ($\because \rho$ and $L$ are constants)

Thus resistance will reduce by 9 times if the radius of the wire is tripled.