Magnetism Flashcards

1
Q

The first magnetic stones were found in ___, near ____

A

Magnesia, Asia Minor.

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2
Q

This stone is called ____

A

magnetite.

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3
Q

The earth’s axis poles(Geographic or “True”
poles) and magnetic poles are not aligned.

True or False

A

True

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4
Q

The _____ is the difference in
alignment between the earth’s magnetic
pole and the axis pole.

A

angle of declination

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5
Q

Natural magnets became
known as ____ or ____

A

“leading stones“
or lodestones.

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5
Q

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

True or False

A

True

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6
Q

There are only three substances that form natural
magnets: ___, ___, and ____

A

iron, nickel, and cobalt.

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7
Q

One theory of magnetism states that electrons spin on their own axis
while orbiting the nucleus

True or False

A

True

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8
Q

This spinning action causes each electron to become a tiny permanent
magnet.

True or False

A

True

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9
Q

The electrons tend to form pairs spinning in opposite directions. These
pairs negate each other’s magnetism.

True or False

A

True

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10
Q

Magnetic materials have some electrons that do not have their
magnetism cancelled in a pair.

True or False

A

True

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11
Q

These magnetic materials (____, ___, and ____) have regions of magnetic
polarity called magnetic ______

A

iron, nickel, and cobalt, domains

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12
Q

When the magnetic domains are in disarray, the material is not magnetic

True or False

A

True

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13
Q

The atoms are disarrayed in a
piece of ____ metal.

A

nonmagnetized

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14
Q

There are 3 classes of magnetic materials:


A

–Ferromagnetic
– Paramagnetic
– Diamagnetic

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15
Q

Ferromagnetic materials are easily magnetized.

True or False

Examples of these materials are ___, ___ , ___ & ___

A

True, iron, nickel, cobalt &
manganese.

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16
Q

Paramagnetic materials are not as easily magnetized.

True or False

Examples are ___, ___, and ____

A

platinum, titanium, and chromium.

17
Q

Diamagnetic materials cannot be magnetized

True or False

18
Q

Diamagnetic materials can be metal or nonmetal.

True or False

  • Magnetic lines of force tend to go around
    diamagnetic materials.
  • Examples of diamagnetic materials are ___, ___, ___, and ____
A

True, copper, brass,
wood, and antimony

19
Q

All magnets have two points opposite each other where the field force is strongest: two points where the magnetic flux is
more dense.
These points are referred to as the magnetic ___.
They are the points at which the magnetic lines of force enter and leave the magnet.
It is not possible to have one ___ without having the other

A

poles, pole

20
Q

The property that opposes the setting up of flux lines is known as ____

A

reluctance.

21
Q

Using this principle, you can construct a path that causes flux to divert around something that you are trying to shield from
magnetic lines of force.
This type of device is called a ____

A

magnetic screen.

22
Q

The magnetic lines of force tend to align and concentrate within the ferromagnetic material.

True or False

This causes poles to be established at the points where the lines of force enter and leave the ferromagnetic material.

This process is referred to as magnetism by ____

A

True, induction.

23
Q

If the ferromagnetic material is
* soft iron (iron with a low carbon content), the iron is easily magnetized. But it loses its magnetism as the
magnetic field is removed.

True or False

24
* hard iron or steel (with a high carbon content), it requires a much stronger magnetic field to be magnetized. However, when the magnetic field is removed, the iron material retains most of its magnetism. True or False
True
25
Ferromagnetic material can be magnetized in several ways. * * *
* Using electric current * Stroking with a magnet * Align and tap
26
If a piece of ferromagnetic material is placed in the coil and a current is passed through the coil in one direction, the magnetic field of the coil causes the domains to align in the ferromagnetic material. True or False
True
27
Another method of producing a magnet is by stroking a piece of ferromagnetic material with a magnet. True or False
True
28
The field of the stroking magnet aligns the domains in the ferromagnetic material, causing it to become magnetized. True or False
True
29
A third, and not very effective way to produce a magnet is to align a piece of ferromagnetic material with any magnetic field, even that of the earth, and tap it lightly. True or False
True
30
The tapping produces enough energy to align some of the domains with the magnetic field, causing the ferromagnetic material to become magnetized. True or False
True
31
There are also several methods for removing magnetism from ferromagnetic materials. * * *
* Using electric current * Using heat * Using vibration
32
When demagnetizing a piece of ferromagnetic material, you use a source of current that changes direction constantly and rapidly. This type of current is called an alternating current(AC) True or False
True
33
If you either slowly remove the material from the coil or slowly reduce the current in the coil, then the field becomes weaker and the domains will be left in a random orientation within the material. True or False
True
34
A very effective method of demagnetization is to apply heat to the magnet. At a certain temperature, called the _____, the molecular structure of the ferromagnetic material rearranges itself and the alignment of the domains is lost even after the material is cooled. True or False
Curie temperature, True
35
Each substance has a different Curie temperature, but for iron it is about ___
770°C.
36
A third way of removing magnetism is by tapping or vibrating the magnet. As the material is magnetized, the domains are moved and the bonds are stressed. When the magnet is vibrated, energy is supplied and the stress tends to restore the domains to their original orientation. The magnetism is lost. True or False
37
Avoid subjecting magnets to conditions that demagnetize them. This means: * do not expose magnets to ___. * do not place magnets near fields created by ___ currents * do not drop magnets or subject them to excessive ____ * do not store magnets near other ____
heat, alternating, vibration, magnets
38
Many types of magnets are stored with a device called a ____ * This is usually a piece of soft iron placed across the poles of the magnet to provide an easy path for the magnetic ___. * If it is not used, the magnetic field will _____ over time.
keeper, flux, weaken
39
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