Question 1

Which of the following best describes the difference between electric field lines and magnetic field lines?

Accepted Answer

Magnetic field lines always form closed loops, while electric field lines begin and end at charges.

Question 2

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 3

Which material is most strongly attracted to a magnet?

Accepted Answer

Iron

Question 4

The SI unit of magnetic field is the Tesla (T). Which of the following is equivalent to 1 Tesla?

Accepted Answer

$$1\ \mathrm{T} = 1\ \mathrm{kg}/(\mathrm{C} \cdot \mathrm{s})$$

Question 5

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

Accepted Answer

$$F = qvB$$

Question 6

Which of the following statements about the force on a charged particle in a magnetic field is correct?

Accepted Answer

The force is always perpendicular to both the velocity and the magnetic field.

Question 7

A proton moves in a circle of radius $$r in a $$uniform magnetic field $$B. $$What is the expression for the radius of its path?

Accepted Answer

$$r = \dfrac{mv}{qB}$$

Question 8

A mass spectrometer separates ions based on their mass-to-charge ratio. If the radius of the ion's path is $$r$$, the magnetic field is $$B$$, and the ion's speed is $$v$$, what is the mass of the ion?

Accepted Answer

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

Question 9

Which of the following best describes the effect of a magnetic field on the kinetic energy of a charged particle?

Accepted Answer

The magnetic field does not change the kinetic energy of the particle.

Question 10

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

Accepted Answer

$$F = ILB$$

Question 11

Two long, parallel wires carry currents $$I_1$$ and $$I_2 in $$the same direction and are separated by a distance $$d. $$What is the force per unit length between the wires?

Accepted Answer

$$\dfrac{\mu_0$ I_1$ I_2$}{2\pi d}$$

Question 12

Which device uses the torque on a current loop in a magnetic field to measure electric current?

Accepted Answer

Galvanometer

Question 13

The magnetic field at the center of a circular loop of radius $$R$$ carrying current $$I is$$:

Accepted Answer

$$B = \dfrac{\mu_0$ I}{2R}$$

Question 14

Ampère’s Law states that the line integral of the magnetic field around a closed path is equal to:

Accepted Answer

$$\mu_0$ times the total current enclosed by the path

Question 15

A solenoid is constructed with $$N$$ turns, length $$l$$, and carries current $$I. $$What is the magnetic field inside the solenoid?

Accepted Answer

$$B = \mu_0$ \dfrac{N}{l} I$$

Question 16

Which of the following best explains why MRI machines use strong magnetic fields?

Accepted Answer

Stronger magnetic fields produce sharper images by aligning more nuclear spins.

Question 17

A rectangular current loop of area $$A$$ and current $$I is $$placed in a uniform magnetic field $$B. $$What is the maximum torque experienced by the loop?

Accepted Answer

$$	au_{max} = IAB$$

Question 18

Which of the following is a consequence of Gauss’ Law for Magnetism?

Accepted Answer

The net magnetic flux through any closed surface is zero.

Question 19

A long straight wire carries a current $$I. $$What is the magnetic field at a distance $$r$$ from the wire?

Accepted Answer

$$B = \dfrac{\mu_0$ I}{2\pi r}$$

Magnetic Fields and Their Applications

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