This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses on “Reactive Power”.

1. The reactive power equation (P_{r}) is?

a) I_{eff}^{2} (ωL)sin2(ωt+θ)

b) I_{eff}^{2} (ωL)cos2(ωt+θ)

c) I_{eff}^{2} (ωL)sin(ωt+θ)

d) I_{eff}^{2} (ωL)cos(ωt+θ)

View Answer

Explanation: If we consider a circuit consisting of a pure inductor, the power in the inductor is reactive power and the reactive power equation (P

_{r}) is P

_{r}=I

_{eff}

^{2}(ωL)sin2(ωt+θ).

2. Reactive power is expressed in?

a) Watts (W)

b) Volt Amperes Reactive (VAR)

c) Volt Ampere (VA)

d) No units

View Answer

Explanation: Reactive power is expressed in Volt Amperes Reactive (VAR) and power is expressed in watts and apparent power is expressed in Volt Ampere (VA).

3. The expression of reactive power (Pr) is?

a) V_{eff}I_{m}sinθ

b) V_{m}I_{m}sinθ

c) V_{eff}I_{eff}sinθ

d) V_{m}I_{eff}sinθ

View Answer

Explanation: The expression of reactive power (P

_{r}) is V

_{eff}I

_{eff}sinθ Volt Amperes Reactive (VAR). Reactive power =V

_{eff}I

_{eff}sinθ Volt Amperes Reactive (VAR).

4. The power factor is the ratio of ________ power to the ______ power.

a) average, apparent

b) apparent, reactive

c) reactive, average

d) apparent, average

View Answer

Explanation: The power factor is the ratio of average power to the apparent power. Power factor =(average power)/(apparent power).

5. The expression of true power (P_{true}) is?

a) P_{a}sinθ

b) P_{a}cosθ

c) P_{a}tanθ

d) P_{a}secθ

View Answer

Explanation: True power is the product of the apparent power and cosθ. The expression of true power (P

_{true}) is P

_{a}cosθ. True power = P

_{a}cosθ.

6. The average power (P_{avg}) is expressed as?

a) P_{a}secθ

b) P_{a}tanθ

c) P_{a}cosθ

d) P_{a}sinθ

View Answer

Explanation: The average power is the product of the apparent power and cosθ. The average power (P

_{avg}) is expressed as P

_{a}cosθ. Average power = P

_{a}cosθ.

7. The equation of reactive power is?

a) P_{a}cosθ

b) P_{a}secθ

c) P_{a}sinθ

d) P_{a}tanθ

View Answer

Explanation: The reactive power is the product of the apparent power and sinθ. The equation of reactive power is P

_{a}sinθ. Reactive power = P

_{a}sinθ.

8. A sinusoidal voltage v = 50sinωt is applied to a series RL circuit. The current in the circuit is given by I = 25sin (ωt-53⁰). Determine the apparent power (VA).

a) 620

b) 625

c) 630

d) 635

View Answer

Explanation: The expression of apparent power (VA) is P

_{app}= V

_{eff}I

_{eff}= (V

_{m}/√2)×(I

_{m}/√2). On substituting the values V

_{m}= 50, I

_{m}=25, we get apparent power = (50×25)/2 = 625VA.

9. Find the power factor in the question 8.

a) 0.4

b) 0.5

c) 0.6

d) 0.7

View Answer

Explanation: In sinusoidal sources the power factor is the cosine of the phase angle between the voltage and the current. The expression of power factor = cosθ = cos53⁰ = 0.6.

10. In the question 8 determine the average power.

a) 365

b) 370

c) 375

d) 380

View Answer

Explanation: The average power, P

_{avg}= V

_{eff}I

_{eff}cosθ. We know the values of V

_{eff}, I

_{eff}are V

_{eff}= 625 and I

_{eff}– 0.6.So the average power = 625 x 0.6 = 375W.

**Sanfoundry Global Education & Learning Series – Network Theory.**

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