MCQ on A.C. Fundamentals and Circuits - Set 05

Practice Test: Question Set - 05


1. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is
    (A) 4 kVAR
    (B) 6 kVAR
    (C) 8 kVAR
    (D) 16 kVAR

2. In a sine wave the slope is constant
    (A) Between 0° and 90°
    (B) Between 90° and 180°
    (C) Between 180° and 270°
    (D) No where

3. The r.m.s. value of pure cosine function is
    (A) 0.5 of peak value
    (B) 0.707 of peak value
    (C) Same as peak value
    (D) Zero

4. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will
    (A) Be reduced by half
    (B) Be doubled
    (C) Be four times at high
    (D) Be reduced to one fourth

5. Capacitors for power factor correction are rated in
    (A) kW
    (B) kVA
    (C) kV
    (D) kVAR

6. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes __________ ohms.
    (A) 2.5
    (B) 5
    (C) 10
    (D) 15

7. For the same peak value which of the following wave will 'have the highest r.m.s. value?
    (A) Square wave
    (B) Half wave rectified sine wave
    (C) Triangular wave
    (D) Sine wave

8. The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of ________ degrees.
    (A) 90
    (B) 60
    (C) 45
    (D) 30

9. Power factor of an inductive circuit is usually improved by connecting capacitor to it in
    (A) Parallel
    (B) Series
    (C) Either (A) or (B)
    (D) None of the above

10. In the case of an unsymmetrical alternating current the average value must always be taken over
    (A) Unsymmetrical part of the wave form
    (B) The quarter cycle
    (C) The half cycle
    (D) The whole cycle

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