Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Circuits > Magnetism > Flashcards

Magnetism Flashcards

1
Q

What are lodestones?

A

Natural magnets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How was the first compass invented?

A

A piece of magnetite was placed on a piece of wood floating in the water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Does magnetic north align with true north?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the angular difference between the true north and the magnetic north?

A

Angle of declination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are permanent magnets?

A

Magnets that do not require any power or force to maintain their field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is one of the most basic laws of magnetism?

A

Energy is required to create a magnetic field, but no energy is required to maintain a magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the three substances that form natural magnets?

A

Iron, nickel, and cobalt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the electron theory of magnetism?

A
  • Electrons spin on their axis which causes a small magnetic field. The electrons spin in opposite directions which causes them to cancel each other out.
  • When atoms of most materials combine, they arrange in a way that cancels the magnetic field. When atoms of iron, cobalt, and nickel combine their magnetic field is added instead of cancelled.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the three classifications of magnetic materials?

A

Ferromagnetic, paramagnetic, and diamagnetic materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are ferromagnetic materials?

A

Metals that are easily magnetized. Ex. Iron, nickel, and cobalt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are paramagnetic materials?

A

Metals that can be magnetized, but not as easily as ferromagnetic materials.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are diamagnetic materials?

A

Metal or nonmetal materials that cannot be magnetized. Ex. copper, brass, antimony.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are magnetic lines of force called?

A

Flux

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

True or False. Magnetic lines of flux repel each other and sometimes cross.

A

False. Magnetic lines of flux repel each other and never cross.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Whenever an electrical current flows through a conductor, a __________ is formed around the conductor.

A

Magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are two factors that determine the number of flux lines produced by an electromagnetic?

A
  1. The number of turns of the wire
  2. The amount of current flow through the wire
17
Q

Strength of electromagnet is proportional to ___________

A

Number of ampere-turns

18
Q

What is permeability?

A

A measurement of a material’s ability to conduct magnetic lines of flux.

19
Q

What is reluctance?

A

A material’s resistance to magnetism

20
Q

What is saturation?

A

The maximum amount of magnetic flux a material can hold.

21
Q

What is residual magnetism?

A

The amount of magnetism left in a material after the magnetizing force has stopped.

22
Q

If the residual magnetism of a piece of core material is hard to remove, the material has a _________

A

High coercive force

23
Q

When is a high coercive force desirable?

A

When you want materials that are intended to be used as permanent magnets.

24
Q

When is a low coercive force desirable?

A

When you want materials that are intended to be used as electromagnets.

25
Q

What is another term used to describe a material’s ability to retain magnetism?

A

Retentivity

26
Q

What are the three different systems used to measure magnetism?

A

The English System, the CGS System, and the MKS or SI system

27
Q

In the English system, magnetic strength is measured in a term called __________.

A

Flux density

28
Q

What term is used to describe the total force producing a magnetic field?

A

Magnetomotive force

29
Q

One line of force is known as a __________ in a CGS system.

A

Maxwell

30
Q

A _____ represents a magnetic force of 1 maxwell per square centimeter or 6.4516 lines of flux per square inch.

A

Gauss

31
Q

In the SI system, the unit of force is _________

A

Newton

32
Q

One newton is equal to how many pounds?

A

0.2248 pounds

33
Q

In SI system, _______ is used to measure magnetic flux

A

Weber

34
Q

One weber = _________ lines of flux

A

100,000,000

35
Q

The main unit of measure in the SI system is the ______

A

Tesla

36
Q

What is the left-hand rule? What can it be used for?

A

When the fingers of the left hand are placed around the windings in the direction of electron current flow, the thumb points north. If the direction of current flow is reversed, the polarity is reversed too.

This rule can be used to figure out the polarity of an electromagnet.

37
Q

What are two ways that a magnet can be demagnetized?

A

Being struck or heated up

38
Q

How does an object become demagnetized?

A

Their molecules become disarranged just like in a non-magnetized object.

39
Q

What is a common device that operates on magnetism?

A

Speakers

Circuits (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions