Q. Two wires that are made up of two different materials whose specific resistance are in the ratio 2 : 3, length 3 : 4 and area 4 : 5. The ratio of their resistances is
A) 6 : 5
B) 6 : 8
C) 5 : 8
D) 1 : 2
Explanation
(c) Resistance $= \rho\frac{l}{A}$
$\therefore\frac{R_{1}}{R_{2}} = \frac{\rho_{1}}{\rho_{2}} \times \frac{l_{1}}{l_{2}} \times \frac{A_{2}}{A_{1}} = \frac{2}{3} \times \frac{3}{4} \times \frac{5}{4} = \frac{5}{8}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.