Question 1

Which of the following actions will NOT induce a current in a wire loop held in a uniform magnetic field with the plane of the loop perpendicular to the field lines?

Accepted Answer

Keeping the orientation of the loop fixed and moving it along the field lines

Question 2

Faraday’s Law of Induction states that the induced emf in a circuit is proportional to which of the following?

Accepted Answer

The rate of change of magnetic flux through the circuit

Question 3

A circular coil of radius $$r = 0.06\ \mathrm{m}$$ and resistance $$R = 2.0\ \Omega is $$placed in a perpendicular magnetic field that increases uniformly from $$B_1 = 0.20$$\ \mathrm{T}$$ to B_2$ = 1.00\ \mathrm{T} in$$ $$\Delta t = 0.50\ \mathrm{s}. $$What is the magnitude of the induced emf?

Accepted Answer

$$\varepsilon = \dfrac{\pi r^2$ (B_2$ - B_1$)}{\Delta t}$$

Question 4

If the magnetic flux through a single loop is given by $$\Phi_B = BA \cos 	heta$$, which of the following will NOT change the flux?

Accepted Answer

Moving the loop parallel to the field lines without changing $$A$$, $$B$$, or $$	heta$$

Question 5

A generator consists of a coil of $$N$$ turns, each of area $$A$$, rotating in a uniform magnetic field $$B$$ with angular velocity $$\omega. $$What is the expression for the peak emf generated?

Accepted Answer

$$\$$varepsilon_0$$ = NAB\omega$$

Question 6

According to Lenz’s Law, the direction of the induced current in a loop is always such that:

Accepted Answer

It opposes the change in magnetic flux through the loop

Question 7

A conducting bar of length $$L$$ moves at velocity $$v$$ perpendicular to a uniform magnetic field $$B. $$What is the motional emf generated across the ends of the bar?

Accepted Answer

$$\varepsilon = B L v$$

Question 8

A rectangular loop moves at constant velocity from a region of higher magnetic field to a region of lower magnetic field. According to Lenz’s Law, what is the direction of the induced current?

Accepted Answer

It is in the direction that restores the original magnetic flux

Question 9

Which of the following best describes the electric field generated by a changing magnetic field in empty space?

Accepted Answer

It is nonconservative

Question 10

A magnet is dropped through a loop of wire. As it falls, the current in the loop:

Accepted Answer

Flows first in a counterclockwise, then in a clockwise direction

Question 11

The general form of Faraday’s Law for a circuit with $$N$$ identical loops is:

Accepted Answer

$$\varepsilon = -N \dfrac{d\Phi_B}{dt}$$

Question 12

Which of the following is a real-world application of eddy currents?

Accepted Answer

Portable metal detectors

Question 13

The induced emf in a loop is related to the line integral of the electric field around the loop by:

Accepted Answer

$$\oint \vec{E} \cdot d\vec{l} = \varepsilon$$

Question 14

A coil with $$N$$ turns and area $$A is $$rotated in a uniform magnetic field $$B at $$angular frequency $$\omega. $$What is the time-dependent emf generated?

Accepted Answer

$$\varepsilon(t) = NAB\omega \sin(\omega t)$$

Question 15

Which statement about the induced electric field due to a changing magnetic field is correct?

Accepted Answer

It can exist even in a vacuum

Question 16

In a charging capacitor, Maxwell introduced the concept of displacement current to resolve which issue in Ampere’s Law?

Accepted Answer

The absence of conduction current between the plates

Question 17

Which equation represents the magnetic flux $$\Phi_B$$ through a surface?

Accepted Answer

$$\Phi_B = \int \vec{B} \cdot d\vec{A}$$

Question 18

A loop of wire is placed in a region where the magnetic field is increasing in time. What is the direction of the induced current according to the right-hand rule?

Accepted Answer

It is in the direction that creates a magnetic field opposing the increase

Question 19

Which of the following is NOT a contribution of Michael Faraday to early electricity?

Accepted Answer

Invention of the battery

Electromagnetic Induction (Chapter 29) – Study Notes

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