Question

A coil consists of 2000 turns of copper wire having a cross-sectional area of 0.8mm². The mean length per turn is 80 em and the resistivity of copper is 0.02μΩ-m. Find the resistance of the coil and power absorbed by the coil when connected across 110 V d.c. supply.

Answer 1

Length of the coil, l = 0.8 x 2000 = 1600m; A = 0.8mm² = 0.8 x 10^-6m²

R = ρ(l/A) = 0.02 x 10^-6 x 1600/0.8 x 10^-6 = 40Ω

Power absorbed = v²/R = 110²/40 = 302.5w