A coil consists of 1000 turns having a cross-sectional area of 0.4 mm². The mean length per turn is 40 cm and the resistivity of the wire is 0.02μΩ-m. The resistance of the coil is _______.

Question

Question

This question was previously asked in

SSC JE Electrical 11 Oct 2023 Shift 3 Official Paper-I

Answer 1

Concept

The resistance of a wire is given by:

\(R=ρ{l× N\over A}\)

where, R = Resistance

ρ = Resistivity

l = Mean length per turn

N = No. of turns

A = Cross-sectional area

Calculation

Given, ρ = 0.02μΩ-m = 0.02 × 10-6 Ω-m

l = 40 cm = 40 × 10-2 m

N = 1000

A = 0.4 mm2 = 0.4 × 10-6 m2

\(R={0.02\times 10^{-6}\times 40\times 10^{2}\times 1000\over 0.4\times 10^{-6}}\)

R = 20 Ω