Question 1

When a bar magnet is cut in half, what happens to its magnetic poles?

Accepted Answer

Each half forms a new dipole, with both a north and south pole.

Question 2

The Earth's geographic north pole is actually which magnetic pole?

Accepted Answer

Magnetic south pole

Question 3

A compass needle placed near a current-carrying wire will:

Accepted Answer

Deflect in a direction that depends on the direction of the current.

Question 4

At each point in space, the direction of the magnetic field vector $$\vec{B} is$$:

Accepted Answer

Tangent to the magnetic field line.

Question 5

Which statement about magnetic field lines around a bar magnet is correct?

Accepted Answer

They point from the north pole to the south pole outside the magnet.

Question 6

The strength of the magnetic force on a charged particle moving in a magnetic field is given by:

Accepted Answer

$$F = qvB \sin \phi$$

Question 7

A positive charge moves perpendicular to a uniform magnetic field. What is the path of the particle?

Accepted Answer

It moves in a circle at constant speed.

Question 8

What is the radius $$R of $$the circular path for a particle of mass $$m$$, charge $$q$$, and speed $$v in a $$magnetic field $$B$$?

Accepted Answer

$$R = \frac{mv}{qB}$$

Question 9

An electron enters a uniform magnetic field perpendicular to its velocity. What is the work done by the magnetic field on the electron?

Accepted Answer

Zero

Question 10

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

Accepted Answer

$$F = I\ell B$$

Question 11

A rectangular current loop is placed in a uniform magnetic field with its plane perpendicular to the field. What does the field exert on the loop?

Accepted Answer

Neither a net force nor a net torque

Question 12

A rectangular current loop is placed in a uniform magnetic field with its plane parallel to the field. What does the field exert on the loop?

Accepted Answer

A net torque

Question 13

The torque $$	au on a $$rectangular current loop of area $$A in a $$uniform magnetic field $$B is $$given by:

Accepted Answer

$$	au = IAB \sin \phi$$

Question 14

The magnetic field at a distance $$r$$ from a long straight wire carrying current $$I is$$:

Accepted Answer

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

Question 15

The magnetic field inside a solenoid of $$n$$ turns per unit length carrying current $$I is$$:

Accepted Answer

$$B = \mu_0$ n I$$

Question 16

A solenoid of length 10 cm has 500 turns and carries 1 A. A solenoid of length 20 cm has 1000 turns and carries 1 A. How does the field inside compare?

Accepted Answer

The same field

Question 17

A metal bar is connected by leads to a battery and placed between the poles of a horseshoe magnet. Just after the switch is closed, what will happen to the bar?

Accepted Answer

It will swing outward, away from the magnet

Question 18

Which of the following best describes the superposition principle for magnetic fields?

Accepted Answer

The total magnetic field is the vector sum of the fields from all sources.

Question 19

A charged particle moves parallel to a uniform magnetic field. What is the magnetic force on the particle?

Accepted Answer

Zero

Question 20

A current-carrying wire produces a magnetic field. What is the direction of the field at a point a distance $$r$$ from the wire?

Accepted Answer

In concentric circles around the wire, as given by the right-hand rule

Magnetic Fields, Forces, and Applications: Study Notes

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