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

Length of the coil, l = 0.8 × 2000 = 1600 m ;

A = 0.8 mm2 = 0.8 × 10−6 m2.

R = lA

ρ = 0.02 × 10−6 × 1600/0.8 × 10−6 = 40 Ω

Power absorbed = V2 / R = 1102/40 = 302.5 W

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