Question

Calculate the ratio of the resistivity of 2 wires having the same length and same resistance with area of cross section 2m^2 and 5m^2 respectively.

(a) 5:7

(b) 2:7

(c) 2:5

(d) 7:5

This question was addressed to me during an online interview.

Enquiry is from Resistivity in chapter Simple DC Networks of Basic Electrical Engineering

Answer 1

Right answer is (c) 2:5

Explanation: Resistivity = R*A/L

Since resistance and length of the two wires are same so resistivity is directly proportional to area of cross section. Ratio of area is 2:5 so the ratio of resistivity is also 2:5.