Question 1

Which of the following best describes the function of an inductor in an electric circuit?

Accepted Answer

It opposes changes in current by inducing an emf proportional to the rate of change of current.

Question 2

The mutual inductance $$M$$ between two coils is defined by which of the following equations?

Accepted Answer

$$M = \frac{N_2$ \Phi_{21}}{I_1$}$$

Question 3

A solenoid has $$N$$ turns, length $$l$$, and cross-sectional area $$A. $$What is the formula for its self-inductance $$L$$?

Accepted Answer

$$L = \mu_0$ \frac{N^2$ A}{l}$$

Question 4

In an LR circuit, the time constant $$	au is $$given by:

Accepted Answer

$$	au = \frac{L}{R}$$

Question 5

Which of the following statements about energy storage in inductors is correct?

Accepted Answer

Inductors store energy in the magnetic field created by the current through them.

Question 6

A current $$I is $$increasing through an inductor of inductance $$L. $$What is the induced emf across the inductor?

Accepted Answer

$$\mathcal{E} = -L \frac{dI}{dt}$$

Question 7

In an LC circuit, the angular frequency of oscillation is given by:

Accepted Answer

$$\omega = \frac{1}{\sqrt{LC}}$$

Question 8

Which of the following best describes the behavior of current in an LR circuit immediately after the switch is closed?

Accepted Answer

The current starts at zero and increases exponentially toward its maximum value.

Question 9

The energy stored in an inductor with inductance $$L$$ and current $$I is$$:

Accepted Answer

$$U = \frac{1}{2} L I^2$

Question 10

In an LRC circuit, the angular frequency of damped oscillations is:

Accepted Answer

$$\omega = \sqrt{\frac{1}{LC} - \frac{R^2$}{4L^2$}}$$

Question 11

A transformer works based on which principle?

Accepted Answer

Mutual inductance between two coils

Question 12

The inductive reactance $$X_L of an $$inductor in an AC circuit is given by:

Accepted Answer

$$X_L = \omega L$$

Question 13

In a phasor diagram for an LRC circuit, which statement is true about the voltage across the inductor relative to the current?

Accepted Answer

The voltage across the inductor leads the current by $$90^\circ.$$

Question 14

Which of the following is a correct statement about the impedance $$Z in a $$series LRC circuit?

Accepted Answer

$$Z = \sqrt{R^2$ + (X_L - X_C)^2$}$$

Question 15

A coaxial cable consists of two concentric cylinders. The inductance per unit length is most directly affected by which of the following?

Accepted Answer

The radii of the inner and outer cylinders and the permeability of the material between them

Question 16

If the current in an inductor is constant, what is the induced emf across the inductor?

Accepted Answer

Zero

Question 17

In an LC circuit, what happens to the energy stored in the system over time (assuming no resistance)?

Accepted Answer

It oscillates between the inductor and the capacitor, but the total energy remains constant.

Question 18

Which of the following best explains why an inductor resists changes in current?

Accepted Answer

A changing current induces a magnetic field, which in turn induces an emf that opposes the change in current.

Question 19

In a real-world application, such as a car ignition system, why are inductors used?

Accepted Answer

To generate a high voltage from a rapidly changing current, which is needed to create a spark.

Question 20

If a circuit contains only a resistor and a capacitor in series (an RC circuit), what happens to the voltage across the capacitor as the circuit reaches steady state?

Accepted Answer

The voltage across the capacitor approaches the supply voltage.

Inductors and Electromagnetic Oscillations in Circuits

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