# Electromagnets

In this worksheet, students will look at how electromagnets work and how we can use them to increase or decrease magnetism. It also includes information about how electromagnets are used.

Key stage:  KS 3

Curriculum topic:   Physics: Electricity and Electromagnetism

Curriculum subtopic:   Magnetism

Difficulty level:

### QUESTION 1 of 10

Electromagnets are made using a coil of wire around an iron core (it can be an iron nail) and letting electricity flow through the wire. Here is a diagram of an electromagnet:

The concept is that the magnetic field around the wire (created by electric current flowing through it) can be strengthened by winding the wire into a coil and twisting around an iron core.

Here are three ways to increase the strength of an electromagnet:

• Increasing the number of coils in the wire
• Increasing the current in the wire
• Using a magnetic material for the core

Have a look at a Maglev train in the picture below:

Electromagnets are used in Maglev trains. A computer system controls the current so the train floats 15cm above the track. The Maglev train is continually pulled forwards, because the electromagnets on the tracks are turned on when they are just in front of the train, so they attract the train. As the train moves, the next set of the electromagnets on the tracks is turned on and pulls the train in turn.

Electric bells also contain an electromagnet. They are used in most schools.

When the current flows through, the electromagnet attracts the hammer. The hammer hits the gong and the bell makes a sound. The current is turned off and the hammer returns to its initial position.

Which is the best description of an electromagnet?

An electromagnet is made from an iron core, a coiled wire and electric current.

An electromagnet is made from an iron core, a normal wire and electric voltage.

An electromagnet is made from a plastic core, a coiled wire and electric current.

Select two uses of electromagnets.

kitchen knives

door bells

Maglev trains

kettles

Select the THREE possible ways of increasing the strength of an electromagnet.

Increase the number of coils.

Use a magnetic material in the core.

Increase the electric current.

Use a narrow core.

Why does the strength of an electromagnet increase when you increase the number of coils?

The strength increases when you coil the wire, so increasing the number of coils would strengthen it further, as it increases the magnetic field.

It decreases the strength of the electromagnet.

It keeps the core closer to the wire.

Why were Maglev trains not invented many years ago?

Computer technology was not advanced enough for the Maglev trains to work many years ago.

There was no need for them.

In the answer box below, write one of the following word(s) to complete the sentence:

Possible words: contact, non-contact, accurate, unsafe

Maglev transport is ________________.

In the answer box below, write the word which completes the following sentence:

The maglev train is continually _________ forward, as the electromagnets on the tracks in front of the train are switched on.

In the answer box below, write the word which completes the following sentence:

The electromagnets on the tracks in front of the train ____________ it and so it keeps on moving.

In the answer box below, write the word which completes the following sentence:

In electric bells, when the current is flowing, the electromagnet attracts the __________.

What makes the sound in an electric bell?

The electromagnet hitting the hammer.

The hammer hitting the gong.

The switch closing and opening.

• Question 1

Which is the best description of an electromagnet?

An electromagnet is made from an iron core, a coiled wire and electric current.
EDDIE SAYS
To make an electromagnet you need an iron core, coiled wire and electric current.
• Question 2

Select two uses of electromagnets.

door bells
Maglev trains
EDDIE SAYS
Electromagnets are used in Maglev trains and electric bells.
• Question 3

Select the THREE possible ways of increasing the strength of an electromagnet.

Increase the number of coils.
Use a magnetic material in the core.
Increase the electric current.
EDDIE SAYS
There are three ways of increasing the strength: increasing the current, increasing the number of coils, using an iron core (magnetic).
• Question 4

Why does the strength of an electromagnet increase when you increase the number of coils?

The strength increases when you coil the wire, so increasing the number of coils would strengthen it further, as it increases the magnetic field.
EDDIE SAYS
A wire with an electric current passing through it generates a magnetic field around it; this is a simple electromagnet. The strength of magnetic field generated is proportional to the amount of current. If we were to increase the number of coils the strength of the magnetic field would increase, also increasing the strength of the magnet.
• Question 5

Why were Maglev trains not invented many years ago?

Computer technology was not advanced enough for the Maglev trains to work many years ago.
EDDIE SAYS
Even though electromagnets were invented some time ago, computer science was not advanced. Maglev trains need advanced computer technology to work accurately and safely.
• Question 6

In the answer box below, write one of the following word(s) to complete the sentence:

Possible words: contact, non-contact, accurate, unsafe

Maglev transport is ________________.

non-contact
non - contact
EDDIE SAYS
It is non-contact, because the train does not touch the tracks but is kept above them.
• Question 7

In the answer box below, write the word which completes the following sentence:

The maglev train is continually _________ forward, as the electromagnets on the tracks in front of the train are switched on.

pulled
EDDIE SAYS
The Maglev train is continually pulled forward as the electromagnets on the tracks in front of the train are switched on.
• Question 8

In the answer box below, write the word which completes the following sentence:

The electromagnets on the tracks in front of the train ____________ it and so it keeps on moving.

attract
EDDIE SAYS
The train is made from magnetic material so when the current is switched on, it is attracted to the electromagnets on the tracks.
• Question 9

In the answer box below, write the word which completes the following sentence:

In electric bells, when the current is flowing, the electromagnet attracts the __________.

hammer
EDDIE SAYS
The hammer is attracted by the electromagnet and hits the gong.
• Question 10

What makes the sound in an electric bell?

The hammer hitting the gong.
EDDIE SAYS
The hammer hits the gong, when attracted by the electromagnet and this produces sound.
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