Magnetism Notes

Question 1

What materials do magnets attract?

Answer 1

Iron, nickel, cobalt and few minerals/alloys

Question 2

Where is the force of a magnet strongest?

Answer 2

At the poles

Question 3

How was the first compass made?

Answer 3

using magnetite on a piece of floating wood in a dish of water

Question 4

What is the North pole of the compass actually referring to?

Answer 4

magnetic south pole of the earth

Question 5

What are the three basic types of magnets?

Answer 5

• Natural
• Artificial
• Electromagnets

Question 6

Example of Natural magnet?

Answer 6

Lodestone (known as magnetite)

Question 7

What is Lodestone?

Answer 7

A natural magnet that is an oxide of iron (Fe3O4) and is still mined today

Question 8

example of a permanent magnet?

Answer 8

Lodestone

Question 9

What do artificial magnets not depend on?

Answer 9

an electrical current to maintain the magnetic field

Question 10

difference between artificial and electromagnetic magnets?

Answer 10

Electromagnets magnetism depends on current flow where artificial does not

Question 11

Ferromagnetic?

Answer 11

metals that are easily magnetized (iron, nickel, cobalt)

Question 12

Paramagnetic?

Answer 12

metals that are not as easily magnetized (platinum, titanium, chromium)

Question 13

Diamagnetic?

Answer 13

metals or non-metal material that can not be magnetized

Question 14

One of the best alloys used for permanent magnets?

Answer 14

Alnico 5

Question 15

What is Alnico 5 made of?

Answer 15

Aluminum, cobalt, nickel, copper, iron

Question 16

What is magnetism caused by?

Answer 16

Static electrical charges (electrostatic lines of force)

Question 17

What direction do flux lines flow?

Answer 17

They exit north and enter south

Question 18

What do flux lines always do?

Answer 18

they always form a complete loop and never cross each other

Question 19

How do flux lines pass through all materials?

Answer 19

Because there is no insulator

Question 20

What is the property that opposes the setting up of flux lines?

Answer 20

reluctance

Question 21

What is used to protect a delicate instrument?

Answer 21

a magnetic screen

Question 22

What is a magnetic screen made of?

Answer 22

soft iron material due to low reluctance

Question 23

What does a magnetic screen do to flux lines?

Answer 23

causes them to bend away from the instrument

Question 24

What determines the amount of magnetic force?

Answer 24

the flux density or concentration

Question 25

The greater concentration of flux lines?

Answer 25

the stronger the magnetic field

Question 26

Flux lines facing the same direction __________ each other?

Answer 26

attract

Question 27

Flux lines facing opposite direction ________ each-other?

Answer 27

repel

Question 28

What happens when a magnet achieves max flux density?

Answer 28

It is said to be saturated

Question 29

Soft iron (low carbon)?

Answer 29

easily magnetized but does not stay magnetized

Question 30

Hard iron (high carbon)?

Answer 30

harder to magnetize but will remain magnetized (permanent magnet)

Question 31

what are the atoms like in non magnetized metals?

Answer 31

disarranged

Question 32

What are atoms like in magnetized metals?

Answer 32

arranged in an orderly fashion (called a domain)

Question 33

How to produce artificial magnets?

Answer 33

- Using DC current - By stroking with a magnet - by tapping the material

Question 34

What is the most effective way to produce artificial magnets?

Answer 34

using DC current

Question 35

Common methods of demagnetizing ferromagnetic material?

Answer 35

- by using heat - by vibration or tapping - by using AC current

Question 36

Most common way to demagnetize ferromagnetic material?

Answer 36

By using AC current to change directions from positive to negative at a rate of 60 cycles per second

Question 37

Precautions to observe to avoid damaging magnets?

Answer 37

- don’t expose magnets to heat - do not place magnets near fields made by AC - do not drop or subject to vibration - has a keeper for horseshoe magnets - do not store magnets near other magnets

Question 38

What is a keeper for?

Answer 38

preserves the strength of a magnet