Power in AC Circuits – Rankers Physics
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Power in AC Circuits

Question 1:

In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An emf
E = E0 cos (wt) applied to the circuit. The power consumed in the circuit is :

\[\frac{E_{0}^{2}}{R}\]
\[\frac{E_{0}^{2}}{2R}\]
\[\frac{E_{0}^{2}}{4R}\]
\[\frac{E_{0}^{2}}{8R}\]
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No solution provided for this question.

Question 2:

An LCR series circuit with a resistance of 100 ohm is connected to an AC source of 200 V
(rms) and angular frequency 300 rad/s. When only the capacitor is removed, the current lags
behind the voltage by 60°. When only the inductor is removed the current leads the
voltage by 60°. The average power dissipated is :

50 W
100 W
200 W
400 W
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No solution provided for this question.

Question 3:

In an a.c. circuit V and I are given by
V = 100 sin (100 t) volts
I = 100 sin (100t + π/3) mA
The power dissipated in the circuit is

\[10^{4} watt\]
10 watt
2.5 watt
5.0 watt
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No solution provided for this question.

Question 4:

A coil has power factor of 0.707 at 60 Hz. Then its power factor at 180 Hz will be :-

\[\frac{1}{\sqrt{2}}\]
\[\frac{1}{\sqrt{5}}\]
\[\frac{1}{\sqrt{10}}\]
\[\sqrt{\frac{5}{2}}\]
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No solution provided for this question.