Question 1

A long straight wire carries a current $$I to $$the right. According to the right-hand rule, what is the direction of the magnetic field directly above the wire?

Accepted Answer

Into the page

Question 2

An electron enters a region with a uniform magnetic field $$\vec{B}$$ pointing into the page. The electron's velocity $$\vec{v} is $$directed to the right. What is the direction of the magnetic force on the electron?

Accepted Answer

Downward

Question 3

Two parallel wires carry currents $$I_1$$ and $$I_2 in $$the same direction. What is the nature of the force between the wires?

Accepted Answer

They attract each other

Question 4

A proton moves in a circle of radius $$r in a $$uniform magnetic field $$B$$ perpendicular to its velocity. Which equation gives the speed $$v of $$the proton?

Accepted Answer

$$v = \dfrac{qBr}{m}$$

Question 5

A rectangular loop of wire is pulled with constant velocity $$v$$ out of a region with a uniform magnetic field $$B ($$perpendicular to the loop). According to Faraday's Law, what is the direction of the induced current in the loop as it leaves the field?

Accepted Answer

Clockwise

Question 6

A solenoid of length $$l$$, with $$N$$ turns and carrying current $$I$$, has a self-inductance $$L. $$Which equation correctly gives $$L$$?

Accepted Answer

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

Question 7

In an $$LR$$ circuit, the current $$I as a $$function of time after the switch is closed is given by which equation?

Accepted Answer

$$I(t) = \dfrac{\mathcal{E}}{R} \left(1 - e$$^{-tR/L}$$\right)$$

Question 8

Which of the following best describes the displacement current?

Accepted Answer

A term added by Maxwell to account for changing electric fields in Ampère's Law

Question 9

The speed of light $$c in $$vacuum is related to the electric permittivity $$\$$varepsilon_0$$ and magnetic permeability $$\$$mu_0 by $$which equation?

Accepted Answer

$$c = \dfrac{1}{\sqrt{\mu_0$ \$$varepsilon_0$$}}$$

Question 10

An electromagnetic wave has a frequency $$f$$ and wavelength $$\lambda. $$Which equation correctly relates the speed $$v of $$the wave to these quantities?

Accepted Answer

$$v = f \lambda$$

Question 11

A 10 cm long solenoid with 1000 turns carries a current of 2 A. What is the energy stored in its magnetic field if its cross-sectional area is $$1 \ \mathrm{cm}^2$$? (Use $$\mu_0$ = 4\pi 	imes 10$$^{-7}$$ \ \mathrm{T \cdot m/A})$$

Accepted Answer

$$U = 0.0126 \ \mathrm{J}$$

Question 12

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

Accepted Answer

$$\mathcal{E} = Blv$$

Question 13

Which of the following statements about Lenz's Law is correct?

Accepted Answer

The induced current always opposes the change in magnetic flux that produced it

Question 14

Which region of the electromagnetic spectrum has the highest photon energy?

Accepted Answer

Gamma rays

Question 15

A laser beam with intensity $$I$$ shines on a perfectly absorbing surface. What is the radiation pressure exerted on the surface?

Accepted Answer

$$P = \dfrac{I}{c}$$

Question 16

A changing magnetic field induces an electric field. Which law describes this phenomenon?

Accepted Answer

Faraday's Law

Question 17

If the current in a solenoid is doubled, what happens to the energy stored in its magnetic field?

Accepted Answer

It increases by a factor of 4

Question 18

A wire loop is placed in a region where the magnetic field is increasing in strength but is directed into the page. What is the direction of the induced current as seen from above?

Accepted Answer

Counterclockwise

Question 19

Which of the following best describes mutual inductance?

Accepted Answer

The property where a changing current in one coil induces an emf in another nearby coil

Magnetism, Electromagnetic Induction, and Electromagnetic Waves: Exam 2 Study Guide

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