Question

If the length and area of cross-section of a conductor are doubled, then its resistance will be

• A. unchanged
• B. halved
• C. doubled
• D. quadrupled

Answer 1

Answer: (A)

unchanged

Answer 2

Initial length of the conductor $l_{1}=l$ Final length of the conductor $I_{2}=2 I$ Initial cross-sectional area $A_{1}=A$ Final cross-sectional area $A_{2}=2 A$ The resistance of conductors given by $R=\rho \frac{1}{A} \propto \frac{1}{A}$ As both the length and area are doubled Hence, there will be no change in the resistance of the conductor and so it will remain unchanged.