Ferromagnetic Cored Inductor in DC Circuit MCQ [Free PDF] – Objective Question Answer for Ferromagnetic Cored Inductor in DC Circuit Quiz

21. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the initial value of the current in the circuit.

A. 5A
B. 10A
C. 0 A
D. 20A

Answer: C

Initially, the inductor behaves as an open circuit for dc current so, i = 0.

 

22. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the final value of the current in the circuit.

A. 5A
B. 10A
C. 15A
D. 20A

Answer: A

The final value of the current in the circuit is:

I = V/R = 5A.

 

23. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the value of current 1s after the switch is closed.

A. 5.44A
B. 4.32A
C. 6.56A
D. 2.34A

Answer: B

We know that:

i = I(1 − eRt/L)

I = V/R = 5A

Substituting the remaining values from the given question, we get i = 4.32A.

 

24. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the value of voltage 1s after the switch is closed.

A. 5.4V
B. 10.8V
C. 0 V
D. 2.7V

Answer: D

V = V0e − Rt/L

V = 20e − 2 = 2.7V.

 

25. Among the following, which is the right formula for decay in an inductive circuit?

A. i = I(1 − e − t/time constant)
B. i = I(1 − et /time constant)
C. i = (1 − e − t /time constant)
D. i = I(e − t /time constant)

Answer: D

The correct formula for decay in an inductive circuit is i = I(e − t /time constant). As the time increases, the current in the inductor decreases and the voltage also increases.

 

26. The discharging time constant of a circuit consisting of an inductor is the time taken for the voltage in the inductor to become __________ % of the initial voltage.

A. 33
B. 63
C. 37
D. 36

Answer: C

We know that: V = V0(e − tR/L).

When t = L/R

we have: V = V0(e − 1) = 0.37 × V0.

Hence the time constant is the time taken for the voltage in an inductive circuit to become 0.37 times its initial voltage.

 

27. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the initial value of the voltage across the inductor.

A. 5V
B. 10V
C. 0 V
D. 20V

Answer: D

Initially, the inductor behaves as an open circuit for dc current so, V = V0 = 20V i.e. same as a voltage source.

 

28. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the final value of the voltage across the inductor.

A. 5V
B. 10V
C. 0 V
D. 20V

Answer: C

At a steady-state, the inductor behaves as a short circuit for dc current so, V = 0

 

29. An RL network is one which consists of ____________

A. Resistor and capacitor in parallel
B. Resistor and capacitor in series
C. Resistor and inductor in parallel
D. Resistor and inductor in series

Answer: D

An R − L network is a network that consists of a resistor that is connected in series to an inductor.

 

30. If the switch is opened at t = 0, what is the current in the circuit?

A. 0A
B. 1A
C. 2A
D. 3A

Answer: C

Initially, when the switch was closed, the current in the inductor was 60/30 = 2A.
The current in the inductor doesn’t change suddenly so when the switch is opened, the current in the inductor remains the same i.e. 2A.

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