Question 1

A compass needle does not always remain parallel to the Earth's surface. What is the primary reason for this behavior?

Accepted Answer

The Earth's magnetic field lines are not always horizontal; they often tilt into the ground, causing the needle to dip.

Question 2

A straight wire carries a current directly away from you. What is the direction of the magnetic field lines surrounding the wire?

Accepted Answer

The field lines form clockwise circles centered on the wire.

Question 3

A horseshoe magnet is held vertically with the north pole on the left and south pole on the right. A wire passing between the poles, equidistant from them, carries a current directly away from you. What is the direction of the force on the wire?

Accepted Answer

Downward

Question 4

Why will a magnet not attract a piece of aluminum foil?

Accepted Answer

Aluminum is not a ferromagnetic material and does not have magnetic domains that can align with the magnet.

Question 5

Two iron bars attract each other no matter which ends are placed close together. What does this indicate about the bars?

Accepted Answer

One is a magnet and the other is not; the magnet induces magnetism in the non-magnet.

Question 6

Why does the magnetic field from household AC wiring usually not affect a compass needle?

Accepted Answer

The AC current changes direction rapidly, so the magnetic field changes too quickly for the compass needle to respond.

Question 7

Refer to the first image. For particle 'a', which is a positive charge moving to the right above a current-carrying wire (current to the right), what is the direction of the magnetic force acting on it?

Accepted Answer

Downward, toward the wire

Question 8

Refer to the second image. Three particles (a, b, c) enter a region with a uniform magnetic field directed into the page. Particle 'a' curves upward, 'b' continues straight, and 'c' curves downward. What can you conclude about the charges of the particles?

Accepted Answer

a is positive, b is uncharged, c is negative

Question 9

Why does a strong magnet held near a CRT television screen cause the picture to become distorted or even go black in some areas?

Accepted Answer

The magnetic field deflects the electron beam, causing electrons to miss their intended spots on the screen.

Question 10

You have three iron rods, two of which are magnets and one is not. Without using any other objects, how can you determine which rods are the magnets?

Accepted Answer

Test all combinations of rod ends; the two rods that repel each other are the magnets.

Question 11

Can a stationary electron be set into motion by a magnetic field? By an electric field? Why or why not?

Accepted Answer

A stationary electron can be set into motion by an electric field, but not by a magnetic field.

Question 12

A charged particle moves in a straight line through a region of space. Which of the following could explain this observation, even if a magnetic field is present?

Accepted Answer

The magnetic field is parallel to the velocity, or there is an electric field that cancels the magnetic force.

Question 13

What is the effect on the magnetic field $$B$$ inside a long solenoid if the diameter of all the loops is doubled, assuming all other factors remain constant?

Accepted Answer

There is no effect; $$B is $$independent of the diameter of the solenoid.

Question 14

What happens to the magnetic field $$B$$ inside a solenoid if the spacing between the loops is doubled, with all other factors unchanged?

Accepted Answer

The magnetic field strength decreases by a factor of 2.

Question 15

In designing a relay, why is an iron rod placed inside a solenoid?

Accepted Answer

The iron rod increases the magnetic field by aligning its domains, making the relay more effective.

Question 16

Which of the following best describes the path of magnetic field lines around a bar magnet?

Accepted Answer

They leave the north pole, travel through space to the south pole, and return inside the magnet to the north pole.

Question 17

Which equation correctly gives the magnitude of the force on a charged particle moving in a magnetic field?

Accepted Answer

$$F = qvB\sin\Theta$$

Question 18

If the length of a solenoid and the total number of loops are both doubled, what happens to the magnetic field $$B$$ inside the solenoid?

Accepted Answer

The magnetic field remains unchanged because the number of loops per unit length stays the same.

Magnetism and Magnetic Fields: Step-by-Step Physics Guidance

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