Ac Fundamentals Circuits And Circuit Theory(Engineering > Electrical Engineering ) Questions and answers for exam Preparation

Question 1. Power factor of an electrical circuit is equal to

R/Z
Cosine of phase angle difference between current and voltage
Ratio of useful current to total current Iw/I
All above

Explanation:-

Answer: Option D. -> All above

Question 2. 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 decrease of resistance
Increase with increase of capacitance and increase of resistance

Explanation:-

Answer: Option D. -> Increase with increase of capacitance and increase of resistance

Question 3. Pure inductive circuit

Consumes some power on average
Does not take power at all from a line
Takes power from the line during some part of the cycle and then returns back to it during other part of the cycle
None of the above

Explanation:-

Answer: Option C. -> Takes power from the line during some part of the cycle and then returns back to it during other part of the cycle

Question 4. The best place to install a capacitor is

Very near to inductive load
Across the terminals of the inductive load
Far away from the inductive load
Any where

Explanation:-

Answer: Option B. -> Across the terminals of the inductive load

Question 5. At very low frequencies a series r-c circuit behaves as almost purely

Resistive
Inductive
Capacitive
None of the above

Explanation:-

Answer: Option C. -> Capacitive

Question 6. Power factor of the system is kept high

To reduce line losses
To maximize the utilization of the capacities of generators, lines and transformers
To reduce voltage regulation of the line
Due to all above reasons

Explanation:-

Answer: Option D. -> Due to all above reasons

Question 7. The equation of 50 hz current sine wave having r.m.s. value of 60 a is

60 sin 25 t
60 sin 50 t
84.84 sin 3141
42.42 sin 314 t

Explanation:-

Answer: Option C. -> 84.84 sin 3141

Question 8. The transient currents are associated with the

Changes in the stored energy in the inductors and capacitors
Impedance of the circuit
Applied voltage to the circuit
Resistance of the circuit

Explanation:-

Answer: Option A. -> Changes in the stored energy in the inductors and capacitors

Question 9. 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

Explanation:-

Answer: Option A. -> Apparent power is more than actual power

Question 10. The inductance of a coil can be increased by

Increasing core length
Decreasing the number of turns
Decreasing the diameter of the former
Choosing core material having high relative permeability

Explanation:-

Answer: Option D. -> Choosing core material having high relative permeability