MCQ
1. Capacitive reactance is more, when-
Capacitance is less and frequency of supply is less
Capacitance is less and frequency of supply is more
Capacitance is more and frequency of supply is less
Capacitance is more and frequency of supply is more
2. The safest value of current the human body can carry for more than 3 second is-
4mA
9mA
15mA
25mA
3. Capacitors for power factor correction are rated in-
kW
kV
KVA
KVAR
4. The frequency of an alternating current is-
The speed with which the alternator runs
The number of cycles generated in one minute
The number of waves passing through a point in one second
The number of electrons passing through a point in one second
5. The time constant of a series R-C circuit is given by-
R/C
RC
RC2
R2C
6. Which of the following statements pertains to resistors only?
Can dissipate considerable amount of power
Can act as energy storage devices
Connecting them in parallel increases the total value
Oppose sudden changes in voltage
7. The double energy transient occur in the-
R-L circuit
R-C circuit
R-L-C circuit
Purely inductive circuit
8. The frequency of domestic power supply in Bangladesh is --
200Hz
60Hz
100Hz
50Hz
9. Skin effect occurs when a conductor carries current at frequencies,
low
High
Very low
Medium
10. --- Power factor of the following circuit will be zeгo.
Resistance
Inductance
Capacitance
Both (b) and (c)
11. Pure inductive circuit-
Consumes some power on average
Does not take power at all from a line
Takes power from the line during some parts of the cycle and then returns back to it during
other parts of the cycle None of the above
12. In a circuit containing R, L. and C, power loss can take place in-
C only
L only
R only
All above
13. In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will-
Be reduced by half
Be doubled
Be four times as high
Be reduced to one fourth
14. The apparent power drawn by an A.C. circuit is 10kVA and active power is 8kW. The reactive power in the circuit is---
4 KVAR
6KVAR
8 KVAR
16 KVAR
15. Time constant of a capacitive circuit-
Increases with the decrease of capacitance and decrease of resistance
Increases with the decrease of capacitance and increase of resistance
Increases with the increase of capacitance and 2 decrease of resistance
Increases with the increase of capacitance and the increase of resistance
16. The purpose of a parallel circuit resonance is to magnify-
Current
Voltage
Power
Frequency
17. In any A.C. circuit always-
Apparent power is more than actual power
Reactive power is more than apparent power
Actual power is more than reactive power
Reactive power is more than actual power
18. Magnitude of current at resonance in R-L-C circuit-
Depends upon the magnitude of R
Depends upon the magnitude of L
Depends upon the magnitude of C
Depends upon the magnitude of R, L and C
19. In a loss-free R-L-C circuit, the transient current is-
Oscillating
Square wave
Sinusoidal
Non-oscillating
20. Pure inductive circuit takes power from the A.C. line, when-
Applied voltage decreases but current increases
Applied voltage increases but current decreases
Both applied voltage and current increase
Both applied voltage and current decrease