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)

Initial length of the conductor
$l_1=l$
Final length of the conductor
$I_2=2I$
Initial cross-sectional area $A_1=A$
Final cross-sectional area $A_2=2A$
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.