This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Alternating Current in an Inductive Circuit”.
1. In case of Inductive circuit, Frequency is ______________ to the inductance.
a) Directly proportional
b) Inversely proportional
d) Much greater than
Explanation: The formula for frequency in an inductive circuit is:
Therefore: XL is directly proportional to f.
2. If the current and voltage are 90 degree out of phase, the power factor will be?
d) Insufficient information provided
Explanation: The power factor is the cosine of the angle in between the voltage and the current. If the angle between the voltage and current is 90, then cos90=0. Hence, the power factor is zero.
3. If the power factor is 10 and the value of inductive reactance is 20 ohm, calculate the resistance in the circuit.
a) 1 ohm
b) 2 ohm
c) 3 ohm
d) 4 ohm
Explanation: We know that:
From the given question, we find that the resistance in the circuit is 2 ohm.
4. What is the unit for inductive reactance?
Explanation: Inductive reactance is nothing but the impedance. Impedance is the AC equivalent of resistance, hence the unit for inductive reactance is ohm.
5. If the current in a coil having a constant inductance of L henrys grows at a uniform rate, what is the value of the average current?
Explanation: The average current is the average of the current which flows in the inductor. Hence it is I/2.
6. Find the average current in an inductor if the total current in the inductor is 26A.
Explanation: Average current= I/2.
Substituting the value of I from the equation, average current= 13A.
7. Calculate the emf induced in an inductor if the inductance is 10H and the current is 2A in 4s.
Explanation: The expression for emf in an inductive circuit is:
Substituting the values from the given question, we get emf= 2.5V.
8. Calculate the current in an inductor if the energy stored is 160J and the inductance is 20H.
Explanation: The expression for energy in an inductor is:
Substituting the values from the given question, we get I=4A.
9. Find the time taken for the current in an inductor to change to 2A from 0A if the power in the inductor is 5W. The value of inductance is 10H.
Explanation: The expression for power in an inductive circuit is:
Substituting the values from the given question, we get t=4s.
10. An induced emf is said to be?
d) Cannot be determined
Explanation: Any circuit in which a change of current is accompanied by a change of flux, and therefore by an induced emf, is said to be inductive.
Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.
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