© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 26 KS4 Physics Electromagnetism

© Boardworks Ltd 20041 of 20 © Boardworks Ltd 20051 of 26

KS4 Physics

Electromagnetism


Electromagnetism

Magnets

Magnetic fields

Summary activities

Electromagnets

Contents


A magnetic material is attracted to magnets and can be made into a magnet.

Magnetic materials

Non-magnetic materials

Which materials are attracted to a magnet?

iron, steel, cobalt and nickel

Magnetic or non-magnetic?

N S

Investigate different materials to find out which are attracted to a magnet and record your results in a table.


How can a magnet be used to separate coins made from steel and coils made from gold?

Steel coins are attracted to a magnet but gold coins are not.

Using magnets to separate coins

N S


Steel is harder to magnetise but does not lose its magnetism easily. Steel is called a

What materials can magnets be made from?

iron, steel, cobalt and nickel

N S

Magnetic materials

Iron is easy to magnetise and also loses its magnetism easily. Iron is called a

Magnets are usually made of steel and other hard magnetic materials because they can retain their magnetism.

soft magnetic material.

hard magnetic material.


Electromagnetism

Magnets

Magnetic fields

Summary activities

Electromagnets

Contents


Where would you find a magnetic field?

What is a magnetic field?


Around every magnet is an invisible force field that will affect all magnetic objects inside it.

The magnetic field of a bar magnet is seen with iron filings.

N S

What does the magnetic field around a bar magnet look like?

strongest field at poles

Where is the magnetic field strongest?

Magnetic field of a bar magnet


Forces between magnets – experiment


repel/attract

repel/attract

repel/attract

Unlike poles attract. Like poles repel.

Repulsion and attraction

N SS N

S NN S

S N S N


1. Magnets are made from which materials? ____________

2. What are the ends of a magnet called? ________

3. What do we call the area around a magnet

where a magnetic force exists? _______________

4. What does the word attract mean? _____________

5. What does the word repel mean? _____________

iron or steel

poles

magnetic field

pull together

push apart

Revising magnetism (1)


6. What will two north poles do if brought together? ______

7. What will two south poles do if brought together? ______

8. What will a north pole and a south pole do

if brought together? _______

9. What materials are attracted by magnets? _____________

10. Is magnetism a contact or non-contact force? ___________

repel

repel

attract

iron and steel

non-contact

Revising magnetism (2)


Electromagnetism

Magnets

Magnetic fields

Summary activities

Electromagnets

Contents


A coil of wire acts like a bar magnet when it has an electric current flowing through it.

One end of the coil becomes a north-seeking pole (N pole). One end of the coil becomes a south seeking pole (S pole).

What is an electromagnet?

This is called an electromagnet.


Apparatus:

batteries

wire

iron nail

What to do:

1. Wrap a coil of wire around the iron nail.

2. Connect the coil of wire to the batteries.

3. See how many paperclips the electromagnet can pick up.

Results:

How many paperclips could the electromagnet pick up?

How could the electromagnet pick up more paperclips?

Making an electromagnet


Investigating electromagnets – experiment


The results for the number of drawing pins attracted to the electromagnet with no core are:

1 2 3

4 2 4 6

8 4 8 12

12 6 12 18

numberof cells

numberof coils

How does changing the current affect the strength of an electromagnet?

How does changing the number of coils affect the strength of an electromagnet?

Investigating electromagnets – results (1)


Nu

mb

er

of

pa

pe

rclip

s

Current (amps)

xx

xx

x x

x

Increasing the number of cells, increases the current, and the number of paperclips picked up by the electromagnet also increases.

The strength of the magnetic field increases

as the current flowing through the coil

increases.

Effect of increasing the current

x


Nu

mb

er

of

pa

pe

rclip

s

Number of turns

xx

xx

x x

x

Increasing the number of turns on the coil, increases the number of paperclips picked up by the electromagnet.

The strength of the magnetic field increases as the number of turns on the coil increases.

Effect of increasing the number of coils

x


Compare the results for the number of drawing pins attracted to the electromagnet with no core and an iron core:

1 2 3

4 2 4 6

8 4 8 12

12 6 12 18

numberof cells

numberof coils

1 2 3

4 6 8 10

8 8 12 16

12 10 16 22

numberof cells

numberof coils

What effect does an iron core have on the strength of an electromagnet?

Investigating electromagnets– results (2)


Compare the results for the number of drawing pins attracted to the electromagnet with no core and a copper core:

1 2 3

4 2 4 6

8 4 8 12

12 6 12 18

numberof cells

numberof coils

1 2 3

4 2 4 6

8 4 8 12

12 6 12 18

numberof cells

numberof coils

What effect does a copper core have on the strength of an electromagnet?

Investigating electromagnets – results (3)


There are three ways to make an electromagnet stronger.What are they?

1. ____________________

2. ____________________

3. ____________________

More turns on the coil

More electrical current

Using an iron core S N

What happens if the position of the battery in the electromagnet circuit is reversed?

The poles on the coil also reverse – north becomes south and south becomes north.

Electromagnets – summary

N S


Electromagnetism

Magnets

Magnetic fields

Summary activities

Electromagnets

Contents


Glossary

core – An object, usually made of iron, which is placed inside the coil of an electromagnet and increases the strength of the magnetic field.

electromagnet – A coil of wire that produces a magnetic field when a current is passed through it.

hard magnetic material – A material that is hard to magnetise but does not lose its magnetism easily.

magnetic field – The invisible force field around a magnet or electromagnet that will affect all magnetic objects within that area.

poles – The parts of a magnet where the magnetic field is strongest.

soft magnetic material – A material that is easy to magnetise and also loses its magnetism easily.


Anagrams


Multiple-choice quiz

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© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 26 KS4 Physics Electromagnetism