Question 1

Which of the following statements best explains why there are no magnetic monopoles in nature?

Accepted Answer

Every magnet always has both a north and a south pole, even if it is broken into smaller pieces.

Question 2

A charged particle moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the magnitude of the force acting on the particle?

Accepted Answer

$$F = qvB$$

Question 3

Which of the following best describes the direction of the magnetic force on a positive charge moving in a magnetic field?

Accepted Answer

It is perpendicular to both the velocity and the magnetic field, as given by the right hand rule.

Question 4

A particle with charge $$q = -5.0 	imes 10$$^{-4}$$ \ \mathrm{C}$$ moves at $$1000 \ \mathrm{m/s} in $$the $$+x$$ direction into a $$0.20 \ \mathrm{T}$$ magnetic field in the $$+y$$ direction. What is the direction of the force on the particle as it enters the field?

Accepted Answer

In the $$-z$$ direction

Question 5

What is the SI unit of the magnetic field $$B$$?

Accepted Answer

Tesla (T)

Question 6

Which of the following equations gives the magnitude of the magnetic field at a distance $$d$$ from a long, straight wire carrying current $$I$$?

Accepted Answer

$$B = \frac{\mu_0$ I}{2\pi d}$$

Question 7

A solenoid is $$0.3 \ \mathrm{m}$$ long with $$1000$$ turns per meter and carries a current of $$5 \ \mathrm{A}. $$What is the magnitude of the magnetic field at the center of the solenoid?

Accepted Answer

$$B = \mu_0$ n I$$

Question 8

Which of the following best explains why some materials are magnetic while others are not?

Accepted Answer

Magnetism is an atomic effect due to electron spin, and in some materials, electron spins do not pair or cancel out, creating magnetic domains.

Question 9

A current-carrying wire of length $$L is $$placed in a uniform magnetic field $$B at an $$angle $$	heta to $$the field. What is the magnitude of the force on the wire?

Accepted Answer

$$F = ILB \sin{	heta}$$

Question 10

Which of the following is a correct application of the right hand rule for the force on a positive charge moving in a magnetic field?

Accepted Answer

Point your fingers in the direction of $$\vec{v}$$, curl them toward $$\vec{B}$$, and your thumb points in the direction of $$\vec{F}.$$

Question 11

A rectangular current loop is placed in a uniform magnetic field. What is the expression for the torque $$	au on $$the loop?

Accepted Answer

$$	au = IAB \sin{	heta}$$

Question 12

Which of the following best describes the path of a charged particle entering a uniform magnetic field at an angle other than $$90^\circ$$?

Accepted Answer

The particle moves in a helical (spiral) path.

Question 13

What is the main cause of the Northern lights (aurora borealis) as explained by the interaction of charged particles and Earth's magnetic field?

Accepted Answer

Charged particles from the sun are trapped by Earth's magnetic field and spiral into the atmosphere, exciting molecules and emitting light.

Question 14

Which of the following is the correct formula for the magnetic field at the center of a circular loop of radius $$r$$ carrying current $$I$$?

Accepted Answer

$$B = \frac{\mu_0$ I}{2r}$$

Question 15

If two long, straight, parallel wires carry current in the same direction, what is the nature of the force between them?

Accepted Answer

They attract each other.

Question 16

A bar magnet is cut in half. What happens to the magnetic poles?

Accepted Answer

Each half has both a north and a south pole.

Question 17

Which of the following best describes the arrangement of magnetic domains in an unmagnetized piece of iron?

Accepted Answer

Domains are randomly oriented, so their fields cancel out.

Question 18

Which of the following is true about the Earth's magnetic field?

Accepted Answer

The south magnetic pole is near the north geographic pole.

Magnetism and Magnetic Fields: Principles and Applications

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