6 Magnetism and electromagnetism

Question 1

What are magnets able to attract?

Answer 1

Objects made from magnetic materials such as iron, steel, nickel, and cobalt, as they are magnetic.

Question 2

What are magnets not able to attract?

Answer 2

Objects made from materials such as plastic, wood, paper, or rubber, as they are non-magnetic.

Question 3

What are the strongest part of a magnet called?

Answer 3

Its poles.

Question 4

What are the poles called?

Answer 4

The North and South poles.

Question 5

What happens if two similar poles are placed near each other?

Answer 5

They repel.

Question 6

What happens if two dissimilar (opposite) poles are placed near each
other?

Answer 6

They attract.

Question 7

What are permanent magnets made out of?

Answer 7

Magnetically hard materials.

Question 8

What is a magnetically hard material?

Answer 8

A material which keeps its magnetism once it has been magnetised.

Question 9

What is an example of a magnetically hard material?

Answer 9

Steel.

Question 10

What are temporary magnets made out of?

Answer 10

Magnetically soft materials.

Question 11

What is a magnetically soft material?

Answer 11

A material which loses its magnetism easily.

Question 12

What is an example of a magnetically soft material?

Answer 12

Iron.

Question 13

What is a magnetic field?

Answer 13

A place where we can detect magnetism around a magnet.

Question 14

What is the method followed when investigating the magnetic field patterns of bar magnets with iron fillings?

Answer 14

1) Place a bar magnet between two books and place a sheet of paper or thin card over it.
2) Sprinkle some iron fillings on the paper above the magnet.
3) Tap the paper very gently.
4) The iron fillings will move to show the magnetic field pattern.
5) Repeat the same experiment using two bar magnets, placing them about 5cm apart.

Question 15

What are some safety precautions needed when investigating the magnetic field patters of bar magnets with iron fillings?

Answer 15

Avoid skin contact with iron fillings, since they irritate the skin. Do not blow them off the paper, because they may get into the eyes, which is very painful.

Question 16

What is the method followed when investigating the magnetic field patterns of bar magnets with small compasses?

Answer 16

1) Place a bar magnet on a piece of paper.
2) Place a large number of small compasses on the paper near the magnet.
3) Look carefully at the pattern shown by the needles of the compasses.
4) Repeat the same experiment using two bar magnets, placing them about 5cm apart.

Question 17

What are magnetic field lines?

Answer 17

A visual tool used to represent magnetic fields.

Question 18

What do magnetic field lines show?

Answer 18

• The shape of the magnetic field.
• The direction of the magnetic force - the field lines ‘travel’ from north to south.
• The strength of the magnetic field - the field lines are closest together where the magnetic field is strongest.

Question 19

How do you draw a magnetic field?

Answer 19

Question 20

What happens if two magnets are placed near eachother?

Answer 20

Their magnetic fields overlap and affect each other.

Question 21

What is special about the magnetic field created between the north pole of one magnet and the south pole of a different magnet?

Answer 21

We will see that the field is shown as a series of straight field lines that are evenly spaced.

Question 22

What is this kind of field called?

Answer 22

As a uniform magnetic field.

Question 23

What exactly is a uniform magnetic field?

Answer 23

Its strength and direction is the same everywhere.

Question 24

What are two examples of uniform magnetic fields?

Answer 24

• Uniform field between the poles of the magnets.
• U-shaped permanent magnets can be used to create a uniform magnetic field.

Question 25

What is an example of induced magnetism?

Answer 25

If we place an object made from a magnetic material, for example, an iron nail, inside a magnetic field it becomes a magnet.

Question 26

What happens in terms of magnetism to magnetically soft materials when their magnetism has been induced?

Answer 26

Its induced magnetism is temporary and disappears if the permanent magnet is removed.

Question 27

What happens in terms of magnetism to magnetically hard materials when their magnetism has been induced?

Answer 27

It will retain some of its magnetism after the magnet is removed.

Question 28

What produces a magnetic field?

Answer 28

An electric current in a conductor.