Question 1

According to Faraday's Law, what is the mathematical expression for the induced EMF ($$\mathcal{E}) in a $$loop due to a changing magnetic flux ($$\Phi_B$$)?

Accepted Answer

$$\mathcal{E} = -\frac{d\Phi_B}{dt}$$

Question 2

A bar magnet is moved into a coil of wire connected to a galvanometer. What is observed and why?

Accepted Answer

A current is induced in the coil because the magnetic flux through the coil is changing.

Question 3

Which of the following best describes Lenz's Law?

Accepted Answer

The induced current creates a magnetic field that opposes the change in magnetic flux.

Question 4

A rod of length $$l$$ moves with velocity $$v$$ perpendicular to a magnetic field $$B. $$What is the induced EMF across the ends of the rod?

Accepted Answer

$$\mathcal{E} = Blv$$

Question 5

Which of the following scenarios will NOT induce a current in a coil of wire?

Accepted Answer

A magnet resting motionless inside the coil.

Question 6

If the magnetic field through a loop is increasing in magnitude and directed into the page, what is the direction of the induced current (as viewed from above)?

Accepted Answer

Counterclockwise

Question 7

A generator produces an alternating voltage described by $$V(t) = V_0$ \sin(\omega t). $$What does the graph of $$V(t)$$ versus $$t$$ look like?

Accepted Answer

A sinusoidal wave oscillating above and below zero

Question 8

Which of the following is a consequence of Maxwell's equations?

Accepted Answer

A time-varying electric field produces a time-varying magnetic field.

Question 9

Which region of the electromagnetic spectrum has the shortest wavelength?

Accepted Answer

Gamma rays

Question 10

A light wave passes through a polarizing filter with its electric field at an angle $$	heta to $$the axis of the filter. What is the transmitted intensity $$I in $$terms of the initial intensity $$I_0$$?

Accepted Answer

$$I = I_0$ \cos^2$ 	heta$$

Question 11

A metal loop is placed near a coil connected to a battery and a switch. Immediately after the switch is closed, what happens in the metal loop?

Accepted Answer

A current is induced in the loop due to the changing magnetic field.

Question 12

Which of the following best explains why eddy currents can cause energy loss in metal objects exposed to changing magnetic fields?

Accepted Answer

Eddy currents generate heat due to electrical resistance in the metal.

Question 13

If unpolarized light of intensity $$I_0$$ passes through two ideal polarizing filters with their axes at $$45^\circ to $$each other, what is the final transmitted intensity?

Accepted Answer

$$I = \frac{I_0$}{2} \cos^2$ 45^\circ$$

Question 14

Which of the following is NOT a property of electromagnetic waves?

Accepted Answer

They require a medium to propagate.

Question 15

A bar magnet is pulled out of a coil connected to a meter. What is observed on the meter?

Accepted Answer

A current is induced in the coil, and the meter shows a deflection.

Question 16

Which of the following best describes the relationship between wavelength ($$\lambda$$), frequency ($$f$$), and the speed of light ($$c) $$for electromagnetic waves?

Accepted Answer

$$c = \lambda f$$

Question 17

A light of intensity $$2.0 W/m$^2$$ passes through a polarizing filter. How should a second filter be oriented to reduce the intensity to $$1.0 W/m$^2$$?

Accepted Answer

At $$45^\circ to $$the first filter

Question 18

Which of the following is a practical application of electromagnetic induction?

Accepted Answer

Electric generators converting mechanical energy to electrical energy

Question 19

Which of the following statements about the electromagnetic spectrum is correct?

Accepted Answer

Radio waves have longer wavelengths than visible light.

Electromagnetic Induction, Spectrum, and Polarization: Chapter 25 Study Notes

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