Magnetism

Question 1

Def ferrous metals

Answer 1

Ferrous metals are metals which contain iron

Question 2

Give 2 properties of ferrous metals

Answer 2

1. Are magnetic

2. Easily corroded

Question 3

What os non ferrous metals

Answer 3

Are metals that do not contain iron

Eg. Aluminium copper lead zinc tin. ( they are non magnetic)

Question 4

Polarity of a magnet

How do we know which side of a magnet is Noth and which side is South

Answer 4

Freely suspended magnets point in a North South direction

The side that points towards the north is called the North seeking pole

The side that points towards the South is called the South seeking pole

Question 5

What happens when a magnet breaks in two

Answer 5

Each half will form a new magnet with same alignment as before

Question 6

State the law of magnetism

Answer 6

Like poles repel and unlike poles attract.

The magnetic forces are produced by interactions between magnetic fields

Question 7

Def Magnetic induction

Answer 7

Magnetic induction is the process whereby a piece of iron is temporarily magnetised by a permanent magnet which is in close proximity to the iron

Question 8

What is meant by a magnetically soft material

Answer 8

It is a material which is easily magnitised and looses it magnetism easily

Question 9

How do one test for a magnet

Answer 9

By using a known magnet and testing if the known magnet can repel the unknown metal. If it repels - then both are magnets

Question 10

Def a magnetic field

Answer 10

magnetic field is the space around a magnet in which the influence of the magnet can be detected

Question 11

Def magnetic field line

Answer 11

magnetic field line is the path along which a north-seeking pole tends to move in a magnetic field

Question 12

Name 7 characteristics of field lines

Answer 12

1. Are symmetrical around axis of the magnet
2. Have a direction from N to S
3. Never cross each other
4. Indicate the strength of the field by the distance between them
5. Extend in 3 dimensions around the magnet
6. Extend outwards from or converge at the poles
7. Are smooth curves

Question 13

Describe the theory of magnetism

Answer 13

1. Magnetic material is made up of small magnetic regions called Domains
2. Domains are formed by groups of atoms which are magnetic because they have spinning electrons
3. Within a domain the spinning electrons are lined up in a way that lines up their magnetic fields in the same direction
   4 If the material is unmagnetised, the directions of the domains are random and their individual magnetic fields cancel the effect of each other
4. If the unmagnetised material is placed in a magnetic field, the majority of the domains line up in the direction of the field and the material is magnetised

Question 14

Name 3 methods of making magnets

Answer 14

1. Stroking magnetic material using a permanent magnet
2. Using a current-carrying coil
3. Tapping a steel bar in a magnetic field

Question 15

Name 3 methods that can demagnetise a magnet

Answer 15

1. Using an alternating current
2. Hammering
3. Heating

Question 16

Name the 3 magnetic elements

Answer 16

Iron
Nickel
Cobalt

Alloys of these elements