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A coil takes a current of 6 A when connected to a 24-V d.c. supply. To obtain the same current with a 50-Hz a.c. supply, the voltage required was 30 V. Calculate (i) the inductance of the coil (ii) the power factor of the coil. |
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Answer» It should be kept in mind the coil offers only resistance to direct voltage whereas it offers impedance to an alternating voltage. ∴ R = 24/6 = 4 Ω; Z = 30/6 = 5Ω (i) ∴ XL = √(Z2 - R2) = √(52 - 42) = 3Ω (ii) p.f. = cos φ = R/Z = 4/5 = 0.8 (lag) |
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