Starter quiz
- An object that always behaves as a magnet is called a __________ magnet.
- permanent ✓
- persistent
- continuous
- constant
- steady
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- Which of the following objects would be attracted to an electromagnet?
- a nickel coin ✓
- a copper nail
- a steel spanner ✓
- an iron pin ✓
- a piece of aluminium foil
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- Which of the following statements explain why soft iron is usually used for the core of an electromagnet?
- Soft iron is a poor conductor of electricity.
- Soft iron is a good conductor of electricity.
- Soft iron is a magnetic material. ✓
- Soft iron becomes magnetised easily. ✓
- Soft iron loses its magnetism easily. ✓
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- Which of the following is a definition of a complete circuit?
- A circuit that contains a battery.
- A circuit that is a closed loop. ✓
- A circuit that includes at least one bulb or resistor.
- A circuit made up of straight sections of wire.
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A pupil has a coil of wire coated in yellow plastic, as shown. They attach metal clips to the ends of the coil and connect them to a suitable battery. Why is there no magnetic field around the coil?- Plastic blocks magnetic fields.
- Plastic is not a magnetic material.
- Plastic is an electrical insulator ✓
- The magnetic fields around the left and right sides of the wire cancel out.
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- A pupil experiments with a bar magnet and an electromagnet. Which of the following statements are correct?
- The bar magnet and electromagnet can repel but cannot attract each other.
- The bar magnet and electromagnet can attract but cannot repel each other.
- The bar magnet and electromagnet can attract and repel each other. ✓
- The bar magnet and electromagnet cannot attract or repel each other.
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Exit quiz
- An electromagnet that loses its magnetism when current stops flowing can also be called a __________ magnet.
- temporary ✓
- part–time
- freelance
- short–term
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- A scrapyard uses an electromagnet to move objects made of a magnetic material such as steel. Which of the following describe an advantage of using an electromagnet compared with a permanent magnet?
- Electromagnets attract all types of metal.
- An electromagnet can be switched off. ✓
- An electromagnet has one pole instead of two.
- An electromagnet has two of the same type of pole.
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Which of the following is the purpose of the springs attached to the bolt of the electromagnetic door lock shown?- They attract the bolt when a current flows in them.
- They are attracted to the electromagnet when a current flows in them.
- They pull the bolt into the door when the electromagnet is switched off. ✓
- They pull the bolt out of the door when the electromagnet is switched off.
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The diagram shows an electric door lock. Which of the following statements are correct?- The door is locked.
- The door is unlocked. ✓
- The electromagnet is switched on. ✓
- The electromagnet is switched off.
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The diagram shows an electric bell. Which of the following happen as the switch is pressed?- The electromagnet stops being magnetised.
- The electromagnet becomes magnetised. ✓
- The clapper moves up with the iron armature. ✓
- The clapper moves down with the iron armature.
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- Which of the following statements describes the function of an electric motor?
- It uses a magnetic field and a current to produce a force. ✓
- It uses a force and a current to produce a magnetic field.
- It uses a magnetic field and a force 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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