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Find supply current, current in each branch and total power factor. [Circuit (dark photograph; values partly illegible in the source scan): an AC source marked "~" at the bottom, labelled approximately "230 V, 50 Hz" (first digits unclear), feeds two…

Q.5 (c) Find supply current, current in each branch and total power factor.

[Circuit (dark photograph; values partly illegible in the source scan): an AC source marked "~" at the bottom, labelled approximately "230 V, 50 Hz" (first digits unclear), feeds two parallel branches. Upper branch: a resistor (read as 10 Ω) in series with an inductor (read as 0.12 H). Lower branch: a resistor (read as 10 Ω) in series with a capacitor (read as 60 μF).]

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Assumed data (values read from the partly illegible figure): V = 230 V, 50 Hz; branch 1: R1 = 10 Ω, L = 0.12 H; branch 2: R2 = 10 Ω, C = 60 μF. Take V = 230∠0° V.

Branch 1: \( X_L = 2\pi(50)(0.12) = 37.70\ \Omega \); \( Z_1 = 10 + j37.70 = 39.00\angle75.14^\circ\ \Omega \).

\( I_1 = \dfrac{230\angle0^\circ}{39.00\angle75.14^\circ} = \) 5.90∠−75.14° A = 1.512 − j5.701 A (pf1 = 0.256 lag).

Branch 2: \( X_C = \dfrac{1}{2\pi(50)(60\times10^{-6})} = 53.05\ \Omega \); \( Z_2 = 10 - j53.05 = 53.99\angle-79.33^\circ\ \Omega \).

\( I_2 = \dfrac{230}{53.99\angle-79.33^\circ} = \) 4.26∠79.33° A = 0.789 + j4.188 A (pf2 = 0.185 lead).

Supply current: \( I = I_1 + I_2 = (1.512 + 0.789) + j(-5.701 + 4.188) = 2.301 - j1.513 \) A = 2.754∠−33.33° A.

Total power factor: cos 33.33° = 0.836 lagging.

Check: P = 230 × 2.754 × 0.8355 = 529.3 W; I1²R1 + I2²R2 = 5.897² × 10 + 4.260² × 10 = 347.7 + 181.5 = 529.2 W ✓.

(The method is unchanged if the printed values differ; with a different supply voltage all currents scale in proportion and the power factor stays the same.)

Doubtly AI · 25 Oct 2026 Flagged for teacher review Report
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