Question 1

A point charge $$q$$ moves with velocity $$\vec{v} in $$space. According to the Biot-Savart law, what is the direction of the magnetic field $$\vec{B} at a $$point $$P$$ relative to the charge's motion?

Accepted Answer

Perpendicular to both $$\vec{v}$$ and the vector $$\vec{r}$$ from $$q to$$ $$P$$

Question 2

Which equation correctly expresses the magnetic field $$\vec{B} at a $$distance $$r$$ from a long, straight wire carrying current $$I$$?

Accepted Answer

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

Question 3

Two parallel wires carry equal currents in opposite directions. What is the nature of the force between them?

Accepted Answer

They repel each other

Question 4

A circular loop of radius $$a$$ carries a current $$I. $$What is the magnetic field at the center of the loop?

Accepted Answer

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

Question 5

Which law is most useful for calculating the magnetic field inside a solenoid with a high degree of symmetry?

Accepted Answer

Ampere's Law

Question 6

A solenoid has $$n$$ turns per unit length and carries a current $$I. $$What is the magnetic field inside the solenoid?

Accepted Answer

$$B = \mu_0$ n I$$

Question 7

What is the force per unit length between two parallel wires separated by distance $$a$$, carrying currents $$I_1$$ and $$I_2$$?

Accepted Answer

$$\frac{\mu_0$ I_1$ I_2$}{2\pi a}$$

Question 8

A current-carrying wire is placed in a magnetic field. Which rule is used to determine the direction of the magnetic field around the wire?

Accepted Answer

Right-hand rule

Question 9

What happens to the magnetic field inside a long, straight wire of radius $$R$$ carrying a uniform current $$I as $$you move from the center to the surface?

Accepted Answer

It increases linearly with $$r$$ until $$r = R$$

Question 10

Which of the following best describes the magnetic field lines around a long, straight current-carrying conductor?

Accepted Answer

They are circles concentric with the wire

Question 11

A toroid has $$N$$ turns and carries a current $$I. $$What is the magnetic field at a distance $$r$$ from the center of the toroid?

Accepted Answer

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

Question 12

Which property distinguishes ferromagnetic materials from paramagnetic and diamagnetic materials?

Accepted Answer

Ferromagnetic materials have permanent atomic magnetic moments that align parallel even in weak external fields

Question 13

What is the effect called when a superconductor expels all magnetic fields from its interior?

Accepted Answer

Meissner effect

Question 14

The SI unit of charge, the coulomb, is defined in terms of the ampere. How much charge passes through a conductor in 1 second if it carries a steady current of 1 ampere?

Accepted Answer

1 coulomb

Question 15

Which equation represents Ampere’s Law for a closed path enclosing a current $$I$$?

Accepted Answer

$$\oint \vec{B} \cdot d\vec{s} = \mu_0$ I$$

Question 16

A current loop has a magnetic moment $$\vec{\mu}. $$Which statement is true about the direction of $$\vec{\mu}$$ for an electron orbiting in a circle?

Accepted Answer

It is opposite to the angular momentum $$\vec{L}$$ due to the negative charge of the electron

Question 17

What happens to a ferromagnetic material when it is heated above its Curie temperature?

Accepted Answer

It becomes paramagnetic

Question 18

Which of the following is NOT a property of diamagnetic materials?

Accepted Answer

They are strongly attracted to magnets

Question 19

The Earth's magnetic field is believed to be generated by which mechanism?

Accepted Answer

Convection currents in the liquid part of the Earth's core

Sources of Magnetic Field: Biot-Savart Law, Ampère’s Law, and Applications

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