Question 1

A long, straight wire carries a current $$I in $$the positive y-direction. What is the magnitude of the magnetic field at a distance $$r$$ from the wire?

Accepted Answer

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

Question 2

Which law is used to calculate the magnetic field produced by a small segment of current-carrying conductor?

Accepted Answer

Biot-Savart Law

Question 3

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

Accepted Answer

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

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

A positive point charge is moving directly toward point P. The magnetic field that the point charge produces at point P:

Accepted Answer

is perpendicular to the line from the point charge to point P.

Question 6

A solenoid has $$n$$ turns per unit length and carries a current $$I. $$What is the magnitude of the magnetic field inside the solenoid (far from the ends)?

Accepted Answer

$$B = \mu_0$ n I$$

Question 7

Which of the following best describes the magnetic field inside a toroidal solenoid of $$N$$ turns, carrying current $$I$$, at a distance $$r$$ from the center?

Accepted Answer

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

Question 8

Two positive point charges move side by side in the same direction with the same velocity. What is the direction of the magnetic force that the upper point charge exerts on the lower one?

Accepted Answer

toward the upper point charge (the force is attractive)

Question 9

A long straight wire lies along the y-axis and carries current in the positive y-direction. A positive point charge moves along the x-axis in the positive x-direction. The magnetic force that the wire exerts on the point charge is in:

Accepted Answer

none of the above

Question 10

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 11

The force per unit length between two parallel conductors carrying equal currents in opposite directions is:

Accepted Answer

repulsive

Question 12

The magnetic field inside a long cylindrical conductor of radius $$R$$ carrying a uniformly distributed current $$I at a $$distance $$r \u003c R$$ from the axis is:

Accepted Answer

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

Question 13

Which of the following is true about the magnetic field lines for a current loop and a bar magnet?

Accepted Answer

They have similar patterns, both forming closed loops.

Question 14

A tightly wound solenoid is used in an MRI machine. If the current through the solenoid is doubled, what happens to the magnetic field inside?

Accepted Answer

It doubles.

Question 15

The Bohr magneton is a physical constant related to which property of the electron?

Accepted Answer

Its orbital magnetic moment

Question 16

Which of the following best describes ferromagnetism?

Accepted Answer

A phenomenon where certain materials exhibit spontaneous magnetization

Question 17

A material exhibits a hysteresis loop when subjected to a changing magnetic field. What does the area inside the loop represent?

Accepted Answer

The energy lost per cycle due to magnetic domain realignment

Question 18

A current $$I$$ flows through a wire of radius $$R. $$What is the current density $$J$$ inside the wire?

Accepted Answer

$$J = \frac{I}{\pi R^2$}$$

Question 19

Which of the following paths will yield a zero value for the line integral $$\oint \vec{B} \cdot d\vec{l}$$ according to Ampère’s Law?

Accepted Answer

A path that does not enclose any net current

Sources of Magnetic Field – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards