DC Theory Lesson 4

Since electrons are charged particles, they will have a(n) ? field around them.

a. diamagnetic

b. ferromagnetic

c. electrostatic

d. permanent

The combination of electrostatic and magnetic fields creates an electromagnetic field.

Select one:

True

False

The magnetic lines around a spinning electron are ? to the electrostatic lines.

a. connected

b. parallel

c. perpendicular

d. none of the above

Most elements and compounds in nature have electrons paired where the spin of one electron is in the opposite direction of the other. This results in the magnetic fields of the electrons canceling each other out. In magnetic materials, there are more electrons spinning in one direction than in the other. This results in a net magnetic field being

created.

Select one:

True

False

When magnetic domains are developed, they will react like small temporary magnets.

Select one:

True

False

Which of the following is not one of the three laws of magnetism?

a. Energy is required to create a magnet (magnetic field), but no energy is required to

maintain a magnet (magnetic field).

b. Like poles repel each other, and unlike poles attract each other.

c. The magnetic force between two poles is directly proportional to the pole strength and

inversely proportional to the square of the distance between them.

d. The magnetic force between two poles is inversely proportional to the pole strength and

directly proportional to the square of the distance between them.

The attraction or repulsion that occurs when magnets are held close to each other is

caused by the ? that flow into and out of a magnet.

a. currents

b. magnetic domains

c. magnetism

d. magnetic lines of force

The flux lines of a magnet leave the south end and enter the north end.

Select one:

True

False

When magnets are arranged with like poles facing each other, the magnets ? each other because the lines of flux are moving in ? directions.

a. attract / opposite

b. attract / same

c. repel / opposite

d. repel / same

When magnets are arranged with opposite poles facing each other, the magnets ? each other because the lines of flux are moving in the ? direction.

a. attract / opposite

b. attract / same

c. repel / opposite

d. repel / same

The ability of a material to focus lines of flux is called ? .

a. electromagnetism

b. electrostatic charges

c. permeability

d. reluctance

Opposition to the passage of flux lines is called ? .

a. permeability

b. relative motion

c. reluctance

d. saturation

Flux lines run perpendicular to each other and will always cross.

Select one:

True

False

Magnetic flux lines are continuous and form closed loops.

Select one:

True

False

Magnetic flux lines periodically cross.

Select one:

True

False

The same number of lines of flux that leave the north pole enter the south pole of a magnet.

Select one:

True

False

Magnetic flux lines try to contract, pulling unlike poles together.

Select one:

True

False

Magnetic lines of force pass through nearly all materials, both magnetic and nonmagnetic.

Select one:

True

False

Magnetic flux lines enter and leave the pole face at right angles, and travel south to north around the magnet.

Select one:

True

False

Flux lines are ? dense at poles, and the magnetic field is ? .

a. less / stronger

b. more / stronger

c. less / weaker

d. more / weaker

Nickel, cobalt, and iron are called ? materials because they are easily magnetized.

a. diamagnetic

b. electromagnetic

c. ferromagnetic

d. paramagnetic

Which of the following is not an example of paramagnetic material that can be magnetized, but not as easily as ferromagnetic materials?

a. Aluminum

b. Chromium

c. Graphite

d. Platinum

e. Titanium

Graphite is an example of a(n) ? material.

a. diamagnetic

b. electromagnetic

c. ferromagnetic

d. paramagnetic

A magnet can be demagnetized by ? or exposing it to a magnetic field caused by a(n)

? .

a. heating / alternating current

b. striking / alternating current

c. striking / direct current

d. a. and b.

e. b. and c.

Flux lines will pass through any material, but they will take the path of least reluctance.

This allows us to ? devices that are adversely affected by magnetic fields.

a. de-magnetize

b. magnetize

c. protect

d. shield

Like poles of a magnet repel, and unlike poles attract.

Select one:

True

False

A material that retains its magnetic properties is called a permanent magnet, and one that loses this characteristic easily when its magnetized force is removed is called a temporary magnet.

Select one:

True

False

A magnet has two poles —the north pole and the south pole.

Select one:

True

False

The north pole of a magnet is designated as follows: If the magnet is free to move, the

end that points to the Earth's South Magnetic Pole is called the north pole of the magnet.

Select one:

True

False

Permanent magnets are made of ? , and temporary magnets are made of soft iron.

a. aluminum

b. copper

c. platinum

d. steel