Chapter 24: Magnetism

Question 1

The source of all magnetism is: a) tiny pieces of iron; b) tiny domains of aligned atoms; c) ferromagnetic materials; d) moving electric charge; e) none of these.

Answer 1

d) moving electric charge

Question 2

Moving electric charges will interact with

Answer 2

an electric field or a magnetic field.

Question 3

An iron rod becomes magnetic when

Answer 3

the net spins of its electrons are in the same direction.

Question 4

Magnetic field lines about a current-carrying wire: a) extend radially from the wire; b) circle the wire in closed loops; c) parallel the length of the wire; d) choices a and b are both correct.

Answer 4

b) circle the wire in closed loops

Question 5

Which pole of a compass needle points to a south pole of a magnet?

Answer 5

north pole

Question 6

An iron nail is more strongly attracted to the

Answer 6

north or south pole–no difference really.

Question 7

Pigeons navigate primarily by

Answer 7

magnetic sensors in their heads.

Pigeons have a magnetic sense, and not only can they discern longitudinal directions along Earth’s magnetic field, they can also detect latitude by the dip of Earth’s field.​

Question 8

The intensity of cosmic rays bombarding the Earth’s surface is largest at the: a) poles; b) mid-latitudes; c) equator.

Answer 8

a) poles

Question 9

Superconducting electromagnets: a) exist now; b) may be possible in the near future; c) may be possible in the distant future; d) are science fiction.

Answer 9

a) exist now

Question 10

If a steady magnetic field exerts a force on a moving charge, that force is directed

Answer 10

at right angles to the direction of the motion.

Question 11

Which force field can accelerate an electron, but never change its speed: a) electric field; b) magnetic field; c) both of these; d) none of these.

Answer 11

b) magnetic field

Question 12

Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a: a) north pole; b) south pole; c) north or south pole–no difference really.

Answer 12

a) north pole

Question 13

Magnetic compasses apparently were first used by: a) Columbus; b) Greeks; c) Australian aborigines; d) Vikings; e) pigeons, then Chinese.

Answer 13

e) pigeons, then Chinese.

Question 14

Magnetic domains normally occur in; a) iron; b) copper; c) silver; d) all of these; e) none of these.

Answer 14

a) iron

Question 15

If a compass is moved from the northern hemisphere to the southern hemisphere, its magnetic needle will change direction: a) by 180 degrees; b) depending on where the measurement is taken; c) by 90 degrees; d) hardly at all; e) none of these.

Answer 15

d) hardly at all

Question 16

Between magnets, it is the attraction of unlike magnetic poles for each other and the repulsion between like magnetic poles (def).

Answer 16

Magnetic force.

In all magnets—can’t have one pole without the other.​ No single pole known to exist.

Question 17

Between a magnetic field and a moving charged particle, it is a deflecting force due to the motion of the particle (def).

Answer 17

Magnetic force

The deflecting force is perpendicular to the velocity of the particle and perpendicular to the magnetic field lines.

Question 18

This force is greatest when the charged particle moves perpendicular to the field lines and is smallest (zero) when it moves parallel to the field lines.

Answer 18

Magnetic force

Question 19

The region of magnetic influence around a magnetic pole or a moving charged particle (def).

Answer 19

Magnetic field

Question 20

Clustered regions of aligned magnetic atoms (def).

Answer 20

Magnetic domains

When these regions themselves are aligned with one another, the substance containing them is a magnet.

Question 21

A magnet whose field is produced by an electric current (def).

Answer 21

Electromagnet

It is usually in the form of a wire coil with a piece of iron inside the coil. Electromagnets without iron cores are used in magnetically levitated, or “maglev,” transportation.

Question 22

Various high-speed particles that travel throughout the universe (def).

Answer 22

Cosmic rays;

The universe is a shooting gallery of charged particles called cosmic rays.

Question 23

A weak and strong magnet repel each other. The greater repelling force is by the: a)​ stronger magnet; b) weaker magnet; c) both the same; d) none of the above.​

Answer 23

c) both the same; (Remember Newton’s third law!)

Question 24

Where magnetic field lines are more dense, the field there is​: a) weaker; b) stronger; c) both A and B; d) neither A nor B.​
​

Answer 24

b) stronger;

Strength indicated by​ closeness of the lines​: lines close together indicates strong magnetic field​; lines farther apart indicates weak magnetic field.

Question 25

The source of all magnetism is​: a) electrons rotating around an atomic nucleus; b) electrons spinning around internal axes; c) either or both A and B; d) tiny bits of iron.

Answer 25

c) either or both A and B

Question 26

What are the two kinds of electron motion which produce a magnetic field?

Answer 26

Electron spin and electron revolution

Question 27

When alignment of domains remains once external magnetic field is removed​?

Answer 27

Permanent magnet​;

Permanent magnets are made by​ placing pieces of iron or similar magnetic materials in a strong magnetic field or by stroking material with a magnet to align the domains..

Question 28

When alignment of domains returns to random arrangement once external magnetic field is removed?

Answer 28

Temporary magnet​

Question 29

Magnetic field forms a pattern of ________ _______ around a current-carrying wire.

Answer 29

concentric circles

Question 30

An electromagnet can be made stronger by​: a) increasing the number of turns of wire; b) increasing the current in the coil; c) both A and B; d) none of the above.

Answer 30

c) both A and B

Question 31

The magnetic field of Earth is not due to a giant magnet in its interior—it is due to

Answer 31

electric currents.

Question 32

Most Earth scientists think that moving charges looping around within the molten part of Earth create the

Answer 32

magnetic field.

Earth’s magnetic field reverses direction: 20 reversals in last 5 million years.​

Question 33

___________ in Earth’s field often allow the ions to dip into the atmosphere, causing it to glow like a fluorescent lamp. Hence the aurora borealis or aurora australis.​

Answer 33

Disturbances

Question 34

Storms on the Sun hurl _______ _________ out in great fountains, many of which pass near Earth and are trapped by its magnetic field.

Answer 34

charged particles

The trapped particles follow corkscrew paths around the magnetic field lines of Earth and bounce between Earth’s magnetic poles high above the atmosphere.​