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An iron-cored choking coil takes 5 A when connected to a 20-V d.c. supply and takes 5 A at 100 V a.c. and consumes 250 W. Determine (a) impedance (b) the power factor (c) the iron loss (d) inductance of the coil. |
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Answer» (a) Z = 100/5 = 20 Ω (b) P = VI cos φ or 250 = 100 × 5 × cos φ ∴ cos φ = 250/500 = 0.5 (c) Total loss = loss in resistance + iron loss ∴ 250 = 20 × 5 + Pi ∴ Pi = 250 − 100 = 150 W (d) Effective resistance of the choke is P/I2 = 250/25 = 10Ω ∴ XL = √(Z2 - R2) = √(400 - 100) = 17.32Ω |
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