Question

Two copper wires of length $l$ and $2 l$ have radii $r$ and $2r$ respectively. What is the ratio of their specific resistances?

• A. 1:02
• B. 2:01
• C. 1:01
• D. 1:03

Answer 1

Answer: (C)

1:01

Answer 2

The specific resistance $(\rho)$ is the characteristic of the material of conductor.
Its value depends only on the material of conductor and its temperature. Its value does not depend on the length and area of cross-section of the conductor.
If a wire is stretched or doubled on itself, it resistance will change, but its specific resistance will remain unaffected.
More conducting the substance, less is its specific resistance.
Note: The value of $\rho$ is more for non- conductors.
For a perfect conductor $\rho =0$ (zero) and for a perfect insulator $\rho =\infty$ (infinite).