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Question

If the current in a coil lags the voltage by 60°, what is the circuit’s power factor?

This question was previously asked in
RRB ALP 2025 CBT 2 Wiremen Question Paper (28-Jul-2026) (Shift 2)
The correct answer is

0.5 lagging

To determine the power factor of the circuit, we need to understand the relationship between the phase angle and power factor.

The power factor (PF) in an AC circuit is given by the cosine of the phase angle (\(\phi\)) between the circuit voltage and current. Mathematically, it is represented as:

\(\text{Power Factor (PF)} = \cos(\phi)\)

Here, the given phase angle is 60°, where the current lags the voltage by 60°. Hence, \(\phi = 60^\circ\).

Now, substituting the value of \(\phi\) into the formula:

\(\text{PF} = \cos(60^\circ)\)

We know from trigonometric values that:

\(\cos(60^\circ) = 0.5\)

This indicates that the power factor is \(0.5\). Since the current lags the voltage, the nature of the power factor is lagging:

The correct answer is: 0.5 lagging.

Let's examine why other options are incorrect:

  • √3/2 leading: This option would apply if the power factor was calculated as √3/2 and leading, which it is not.
  • √3/2 lagging: Similarly, this is incorrect as our calculation showed the power factor as 0.5, not √3/2.
  • 0.5 leading: This would occur if the phase angle was -60°, resulting in a leading power factor, which is not the case here.

Hence, the final answer aligns with the given correct answer.

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Similar Questions

  1. If voltage is measured across an AC mains open switch, the meter will read:

  2. What is the relation between line voltage and phase voltage in a delta connection?

  3. If the value of phase voltage in a star connected circuit is 240 V, then its line voltage is ______.

  4. In which of the following connections do we have common neutral point?

  5. What is meant by line voltage?

  6. If apparent power is found equal to active power, then the system power factor is:

  7. When a capacitor load is connected, the power factor is:

  8. When an inductive load is connected, the power factor is:

  9. To find real power, the apparent power has to be multiplied by:

  10. For a system with 230 V AC, 5 A current and lag of 30°, what's the reactive power?


Important Questions from Alternating Current

  1. If voltage is measured across an AC mains open switch, the meter will read:

  2. The frequency of an alternating current is 3 Hz. It implies that
  3. What is the relation between line voltage and phase voltage in a delta connection?

  4. If the value of phase voltage in a star connected circuit is 240 V, then its line voltage is ______.

  5. In which of the following connections do we have common neutral point?

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