New
New
Year 9

Using electromagets

I can describe how electromagnets are used in cranes, locks, bells and motors.

New
New
Year 9

Using electromagets

I can describe how electromagnets are used in cranes, locks, bells and motors.

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Lesson details

Key learning points

  1. An electromagnetic door lock uses an electromagnet to pull a magnetic bolt to unlock a door.
  2. An electric bell often contains an electromagnet that attracts and moves the striker, making it hit the bell.
  3. As an electromagnet moves the striker in an electric bell, it breaks its own circuit to let the striker spring back.
  4. A motor contains a spinning coil of wire that is an electromagnet.
  5. When there is a current in the spinning coil of wire in a motor, other magnets around it will push it round.

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.

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.

Video clips can be found online that show you how to make the simple motor suggested in task B by searching for ‘paperclip motor’.
Teacher tip

Equipment

Insulated wire, AAA battery, 2 safety pins, insulating tape, neodymium magnet and sandpaper.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
An object that always behaves as a magnet is called a __________ magnet.
Correct answer: permanent
persistent
continuous
constant
steady
Q2.
Which of the following objects would be attracted to an electromagnet?
Correct answer: a nickel coin
a copper nail
Correct answer: a steel spanner
Correct answer: an iron pin
a piece of aluminium foil
Q3.
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.
Correct answer: Soft iron is a magnetic material.
Correct answer: Soft iron becomes magnetised easily.
Correct answer: Soft iron loses its magnetism easily.
Q4.
Which of the following is a definition of a complete circuit?
A circuit that contains a battery.
Correct answer: 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.
Q5.
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?
An image in a quiz
Plastic blocks magnetic fields.
Plastic is not a magnetic material.
Correct answer: Plastic is an electrical insulator
The magnetic fields around the left and right sides of the wire cancel out.
Q6.
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.
Correct answer: The bar magnet and electromagnet can attract and repel each other.
The bar magnet and electromagnet cannot attract or repel each other.

6 Questions

Q1.
An electromagnet that loses its magnetism when current stops flowing can also be called a __________ magnet.
Correct answer: temporary
part–time
freelance
short–term
Q2.
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.
Correct answer: An electromagnet can be switched off.
An electromagnet has one pole instead of two.
An electromagnet has two of the same type of pole.
Q3.
Which of the following is the purpose of the springs attached to the bolt of the electromagnetic door lock shown?
An image in a quiz
They attract the bolt when a current flows in them.
They are attracted to the electromagnet when a current flows in them.
Correct answer: 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.
Q4.
The diagram shows an electric door lock. Which of the following statements are correct?
An image in a quiz
The door is locked.
Correct answer: The door is unlocked.
Correct answer: The electromagnet is switched on.
The electromagnet is switched off.
Q5.
The diagram shows an electric bell. Which of the following happen as the switch is pressed?
An image in a quiz
The electromagnet stops being magnetised.
Correct answer: The electromagnet becomes magnetised.
Correct answer: The clapper moves up with the iron armature.
The clapper moves down with the iron armature.
Q6.
Which of the following statements describes the function of an electric motor?
Correct answer: 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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