This set of Basic Electrical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Energy Stored in an Inductor”.

1. 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?

a) I

b) I/2

c) I/4

d) 0

View Answer

Explanation: The average current is the average of the current which flows in the inductor. Hence it is I/2.

2. What is the power in the magnetic field if the current in a coil has a constant inductance of L henrys grows at a uniform rate?

a) LI/2t

b) LI^{2}/2t

c) L/2It

d) L/2I^{2}t

View Answer

Explanation: EMF induced in the coil is Ldi/dt.

Energy=ei*dt=Lidi/dt*dt=Li

^{2}/2.

Power=Energy/Time = Li

^{2}/2t.

3. What is the energy stored in the magnetic field if the current in a coil has a constant inductance of L henrys grows at a uniform rate?

a) LI/2

b) LI^{2}/2

c) L/2I

d) L/2I^{2}

View Answer

Explanation: EMF induced in the coil is Ldi/dt.

Energy=ei*dt=Lidi/dt*dt=Li

^{2}/2.

4. Find the average current in an inductor if the total current in the inductor is 26A.

a) 10A

b) 26A

c) 13A

d) 5A

View Answer

Explanation: Average current = I/2.

Substituting the value of I from the equation, average current = 13A.

5. Calculate the power in an inductive circuit if the inductance is 10H, the current flowing in the inductor is 2A in 4s.

a) 50W

b) 4W

c) 5W

d) 10W

View Answer

Explanation: The expression for power in an inductive circuit is:

P = LI

^{2}/2t

Substituting the values from the given question, we get P=5W.

6. Calculate the value of stored energy in an inductor if the value of inductance is 20H and 4A of current flows through it.

a) 220J

b) 150J

c) 190J

d) 160J

View Answer

Explanation: The expression for energy in an inductor is

E = LI

^{2}/2. Substituting the values from the given question, we get E = 160J.

7. Calculate the emf induced in an inductor if the inductance is 10H and the current is 2A in 4s.

a) 2.5V

b) 1.5V

c) 3.5V

d) 5V

View Answer

Explanation: The expression for emf in an inductive circuit is:

emf = LdI/dt

Substituting the values from the given question, we get emf = 5V.

8. Calculate the value of emf in an inductor if the value of inductance is 15H and an average current of 5A flows through it in 10s.

a) 15V

b) 7.5V

c) 10V

d) 5.5V

View Answer

Explanation: The expression for emf in an inductive circuit is:

emf = LdI/dt

Substituting the values from the given question, we get emf = 7.5V.

9. Calculate the current in an inductor if the energy stored is 160J and the inductance is 20H.

a) 1A

b) 2A

c) 3A

d) 4A

View Answer

Explanation: The expression for energy in an inductor is:

E = LI

^{2}/2

Substituting the values from the given question, we get I=4A.

10. 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.

a) 1s

b) 2s

c) 3s

d) 4s

View Answer

Explanation: The expression for power in an inductive circuit is:

P = LI

^{2}/2t

Substituting the values from the given question, we get t=4s.

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