Magnetism

Question 1

Permanent magnets

Answer 1

a magnet that retains its magnetism even after removal of magnitising force (such as steel)

Question 2

hard magnetic materials

Answer 2

magnetic materials that can be permanently magnetised

Question 3

examples of hard magnetic materials

Answer 3

alloys of iron, nickel and cobalt

Question 4

soft magnetic material

Answer 4

magnetic materials that are only temporariliy magnetised

Question 5

example of soft magnetic materia

Answer 5

iron

Question 6

ferrous

Answer 6

a material that contains iron

Question 7

electromagnet

Answer 7

consist of a coil of wire wrapped around a magnetically soft core and can be turned on and off with a current

Question 8

methods of magnetisation

Answer 8

1. Stroke the material with a magnet
2. coil of wire with current flowing through (electromagnet)
3. hammer them inside a magnetic field

Question 9

methods of demagnetisation

Answer 9

1. hitting it with a hammer
2. heating them
3. place an object inside a coil of wire with an alternating current and remove the object

Question 10

the curie point

Answer 10

when an object loses it’s magnetisation (permanent)

Question 11

what causes magnetism

Answer 11

Caused by moving charges

Question 12

permanent magnet uses

Answer 12

Compasses, School lab experiments, toys, fridge magnets

Question 13

electromagnet uses

Answer 13

MRI scanners - produces diagnostic images of organs
Speakers and earphones - use electromagnets to sense or send sound waves
Recyling - seperate metals from other materials
Mag-Lev trains - hovering reduces friection and allows extremely high speeds

Question 14

magnetic materials

Answer 14

can repel and attract other magnetic materials

Question 15

unmagnetised materials

Answer 15

only attract, not repulse
- a magnet can only repel another magnet

Question 16

how to test if a material is a magnet

Answer 16

bring it close to a known magnet.
- if can be repelled then the material itself is a magnet
- if only attracted and not repelled, then it is a magnetic material

Question 17

types of magnets

Answer 17

permanent magnets
induced magnets

Question 18

how can a magnetic material be induced

Answer 18

when the magnetic material is placed in a magnetic field - the material can be a magnet temporarily

Question 19

magnetic field

Answer 19

a region around a magnet where a force acts on another magnet or on a magnetic material
- all magnets are surrounded by this field

Question 20

magnetic field lines

Answer 20

used to represent strength (shown in distance between lines) and direction (shown in arrows) of a magnetic field
- north to south
- must never touch or cross other field lines

magnets are strongest at the poles; the magnetic field lines are closest together