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 galvanometer during the motion?

Accepted Answer

The changing magnetic flux through the coil induces an emf according to Faraday's Law.

Question 2

In the experiment shown in the second image, what happens to the galvanometer reading when the switch is closed and why?

Accepted Answer

The galvanometer briefly deflects, indicating an induced emf due to the changing magnetic flux.

Question 3

Which of the following best describes the condition for maximum magnetic flux through a loop, as illustrated in the fifth image?

Accepted Answer

The magnetic field is perpendicular to the plane of the loop.

Question 4

Given the formula $$\$$\mathcal{E} = -\frac{\Delta \Phi_B}{\Delta t}\$ (shown in the seventh image), what does the negative sign represent?

Accepted Answer

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

Question 5

A circular coil is rotated in a uniform magnetic field as shown in the tenth image. At which orientation is the induced emf in the coil zero?

Accepted Answer

When the plane of the coil is parallel to the magnetic field.

Question 6

A metal rod of length $$\ell$$ moves with velocity $$v$$ perpendicular to a magnetic field $$B ($$see the twelfth image). What is the magnitude of the induced emf across the rod?

Accepted Answer

$$\B$$\ell v\$

Question 7

In an electric generator, mechanical energy is converted to electrical energy. Which component ensures that the output is alternating current (AC)?

Accepted Answer

Slip rings

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? Use $$\$$\frac{V_S}{V_P} = \frac{N_S}{N_P}\$.

Accepted Answer

600 V

Question 9

Which of the following is a practical application of electromagnetic induction for safety in household wiring?

Accepted Answer

Ground Fault Circuit Interrupter (GFCI)

Question 10

In an LR circuit, the time constant $$\$$	au\$$ is given by $$\$$	au = \frac{L}{R}\. $$What does the time constant physically represent?

Accepted Answer

The time for the current to reach about 63% of its maximum value after the switch is closed.

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 are in the secondary coil?

Accepted Answer

1200 turns

Question 12

Which of the following statements about eddy currents is correct?

Accepted Answer

Eddy currents are induced in bulk conductors and can cause energy loss as heat.

Question 13

A DRAM chip loses its information when power is turned off. What is this type of memory called?

Accepted Answer

Volatile memory

Question 14

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

Accepted Answer

$$\X_L = X_C$$\$

Question 15

Which equation correctly expresses the energy density stored in a magnetic field?

Accepted Answer

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

Question 16

A microphone works by electromagnetic induction. Which part of the microphone is responsible for generating the induced emf?

Accepted Answer

The vibrating membrane moving a coil in a magnetic field

Question 17

If the current in the primary coil of a transformer changes rapidly, what happens in the secondary coil?

Accepted Answer

An emf is induced in the secondary coil due to mutual inductance.

Question 18

Which of the following best explains why AC (alternating current) is used for long-distance power transmission?

Accepted Answer

Transformers require changing current to operate efficiently.

Question 19

A patient’s blood velocity is measured using the principle of electromagnetic induction. If the blood vessel has a diameter $$\ell = 0.01 m$$, the magnetic field $$B = 0.2 T$$, and the measured emf is $$2 	imes 10$$^{-4}$$ V, what is the velocity of the blood? Use $$\$$\mathcal{E} = B\ell v\$.

Accepted Answer

0.1 m/s

Electromagnetic Induction and Faraday’s Law: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard