Question 1

A bar magnet is moved rapidly into a coil connected to a galvanometer, as shown in the first image. What is the primary reason a current is observed in the coil only when the magnet is moving?

Accepted Answer

A current is induced only when the magnetic field inside the coil is changing.

Question 2

Which of the following best describes Faraday’s Law of Induction?

Accepted Answer

The induced emf in a circuit is equal to the negative rate of change of magnetic flux through the circuit.

Question 3

Given the formula $$\mathcal{E} = -\frac{\Delta \Phi_B}{\Delta t}$$, what does the negative sign represent?

Accepted Answer

It indicates that the induced emf opposes the change in magnetic flux (Lenz’s Law).

Question 4

A circular loop of wire with area $$A is $$placed in a uniform magnetic field $$B at an $$angle $$	heta to $$the field. What is the expression for the magnetic flux through the loop?

Accepted Answer

$$\Phi_B = BA \cos 	heta$$

Question 5

A rectangular coil is rotated in a uniform magnetic field. At which orientation is the magnetic flux through the coil maximum?

Accepted Answer

When the plane of the coil is perpendicular to the magnetic field lines.

Question 6

A metal rod of length $$\ell$$ moves with velocity $$v$$ perpendicular to a uniform magnetic field $$B. $$What is the induced emf across the ends of the rod?

Accepted Answer

$$\mathcal{E} = B \ell v$$

Question 7

Which of the following statements about electric generators is correct?

Accepted Answer

They convert mechanical energy into electrical energy using electromagnetic induction.

Question 8

A transformer has 100 turns on the primary coil and 500 turns on the secondary coil. If the input voltage is 120 V, what is the output voltage?

Accepted Answer

600 V

Question 9

Why are eddy currents considered undesirable in the cores of transformers and electric motors?

Accepted Answer

They cause energy losses due to heating.

Question 10

In an LR circuit, the time constant $$	au is $$given by which of the following expressions?

Accepted Answer

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

Question 11

A step-up transformer increases the voltage from 120 V to 2400 V. If the primary coil has 60 turns, how many turns does the secondary coil have?

Accepted Answer

1200 turns

Question 12

Which device uses electromagnetic induction to interrupt current flow in the event of a ground fault, thereby preventing electrocution?

Accepted Answer

Ground Fault Circuit Interrupter (GFCI)

Question 13

The energy density stored in a magnetic field is given by which of the following formulas?

Accepted Answer

$$u = \frac{1}{2} \frac{B^2$}{\mu_0$}$$

Question 14

In an AC circuit containing only a capacitor, how does the current relate to the voltage?

Accepted Answer

The current leads the voltage by 90°.

Question 15

A coil with $$N$$ turns is placed in a time-varying magnetic field. Which equation gives the induced emf?

Accepted Answer

$$\mathcal{E} = -N \frac{\Delta \Phi_B}{\Delta t}$$

Question 16

Which of the following is a real-world application of mutual inductance?

Accepted Answer

A transformer transferring energy between two coils.

Question 17

In a series LRC AC circuit, what is the condition for resonance?

Accepted Answer

The inductive reactance equals the capacitive reactance: $$X_L = X_C$$

Question 18

A hard drive stores information by:

Accepted Answer

Magnetizing small regions on a ferromagnetic coating.

Question 19

Which of the following best describes the function of a microphone based on electromagnetic induction?

Accepted Answer

A vibrating membrane moves a coil in a magnetic field, inducing an emf.

Electromagnetic Induction and Faraday’s Law: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard