Starter quiz
- A single loop of wire in a coil is also called a __________.
- ring
- turn ✓
- hoop
- round
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- A piece of unmagnetised steel would be attracted to __________ of an electromagnet.
- both ends ✓
- neither of the ends
- only the north-seeking end
- only the south-seeking end
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- Some magnetic materials are described as ‘soft’. Which of the following statements about a soft magnetic material is correct?
- It is easy to magnetise and easy to demagnetise. ✓
- It is easy to magnetise and hard to demagnetise.
- It is hard to magnetise and easy to demagnetise.
- It is hard to magnetise and hard to demagnetise.
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- An electromagnet is made by winding a wire around a soft iron core. Which of the following is necessary for the electromagnet to work?
- using wire made of a non-magnetic material
- using wire made of a soft magnetic material
- using wire made of a magnetic material (which does not have to be soft)
- using wire that is insulated ✓
- using wire that is not insulated
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- A coil of wire carries a current of 0.5 A. Which of the following changes would increase the strength of the magnetic field around the wire?
- adding a copper core
- adding an aluminium core
- changing the current to 0.7 A ✓
- moving the turns of the coil closer together ✓
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- An electromagnet with a pure iron core is used to pick up small pieces of steel. Which of the following statements explain why some pieces stay stuck to the electromagnet after it is switched off?
- Steel is a soft magnetic material.
- Steel is a hard magnetic material. ✓
- The iron core stays magnetised.
- The pieces of steel stay magnetised. ✓
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Exit quiz
- A magnet that never loses its magnetism is called a permanent magnet. An electromagnet that loses its magnetism when current stops flowing is called a ______ magnet.
- 'temporary' ✓
The diagram shows an electric bell. Match each label with the name of the part.- A⇔switch ✓
- B⇔bell ✓
- C⇔electromagnet ✓
- D⇔clapper ✓
- E⇔armature ✓
The diagram shows an electric bell. Which of the following statements are correct?- The electromagnet does not move. ✓
- The spring pushes upwards on the armature.
- The spring pulls downwards on the armature. ✓
- The circuit is complete for all of the time that the switch is held down.
- When the circuit is complete, current flows between the clapper and the bell.
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The diagram shows an electric bell. A person holds the switch down. Which of the following statements are correct?- Each time the armature moves up, the circuit is broken. ✓
- Each time the armature moves down, the circuit is broken.
- Each time the circuit is broken, the spring moves the armature up.
- Each time the circuit is broken, the spring moves the armature down. ✓
- Each time the circuit is completed, the spring moves the armature down.
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The diagram shows an electromagnetic door lock. Which of the following statements are correct?- The bolt is made of steel.
- The bolt is made of soft iron. ✓
- The door is locked while the electromagnet is switched on.
- The door is unlocked while the electromagnet is switched on. ✓
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- Which of the following statements is correct?
- An electric motor uses a current in a magnetic field to produce a force. ✓
- An electric motor uses a force acting on a current to produce a magnetic field.
- An electric motor uses a force acting on a magnetic field to produce a current.
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- An electromagnetic door lock uses an electromagnet to pull a magnetic bolt to unlock a door.
- An electric bell often contains an electromagnet that attracts and moves the striker, making it hit the bell.
- As an electromagnet moves the striker in an electric bell, it breaks its own circuit to let the striker spring back.
- A motor contains a spinning coil of wire that is an electromagnet.
- When there is a current in the spinning coil of wire in a motor, other magnets around it will push it round.
Common misconception
It is very common for pupils to think that uninsulated wire is needed for the coil of an electromagnet.
When discussing an electromagnet, always refer to the insulated wire in its core, which is necessary so the current in each turn adds to the strength of the electromagnet.
Keywords
Electromagnet - A magnet made by running current through a coil of wire round an iron core.
Temporary magnet - An electromagnet that loses its magnetism when current stops flowing through it.
Electric lock - A lock that can be opened with an electromagnet when a switch is closed.
Electric bell - A bell that uses an electromagnet to strike a clapper on the bell and which resets itself to keep ringing.
Electric motor - A motor that uses a magnetic field to produce a force.
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