New
New
Year 11
OCR
Higher

Applications of electromagnets

I can describe how electromagnets are used in a range of practical applications.

New
New
Year 11
OCR
Higher

Applications of electromagnets

I can describe how electromagnets are used in a range of practical applications.

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.

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.

Video clips can be found online that show you how to make the simple motor suggested in task B by searching for ‘paper clip 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).

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6 Questions

Q1.
A single loop of wire in a coil is also called a __________.
ring
Correct answer: turn
hoop
round
Q2.
A piece of unmagnetised steel would be attracted to __________ of an electromagnet.
Correct answer: both ends
neither of the ends
only the north-seeking end
only the south-seeking end
Q3.
Some magnetic materials are described as ‘soft’. Which of the following statements about a soft magnetic material is correct?
Correct answer: 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.
Q4.
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)
Correct answer: using wire that is insulated
using wire that is not insulated
Q5.
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
Correct answer: changing the current to 0.7 A
Correct answer: moving the turns of the coil closer together
Q6.
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.
Correct answer: Steel is a hard magnetic material.
The iron core stays magnetised.
Correct answer: The pieces of steel stay magnetised.

6 Questions

Q1.
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.
Correct Answer: temporary
Q2.
The diagram shows an electric bell. Match each label with the name of the part.
An image in a quiz
Correct Answer:A,switch

switch

Correct Answer:B,bell

bell

Correct Answer:C,electromagnet

electromagnet

Correct Answer:D,clapper

clapper

Correct Answer:E,armature

armature

Q3.
The diagram shows an electric bell. Which of the following statements are correct?
An image in a quiz
Correct answer: The electromagnet does not move.
The spring pushes upwards on the armature.
Correct answer: 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.
Q4.
The diagram shows an electric bell. A person holds the switch down. Which of the following statements are correct?
An image in a quiz
Correct answer: 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.
Correct answer: Each time the circuit is broken, the spring moves the armature down.
Each time the circuit is completed, the spring moves the armature down.
Q5.
The diagram shows an electromagnetic door lock. Which of the following statements are correct?
An image in a quiz
The bolt is made of steel.
Correct answer: The bolt is made of soft iron.
The door is locked while the electromagnet is switched on.
Correct answer: The door is unlocked while the electromagnet is switched on.
Q6.
Which of the following statements is correct?
Correct answer: 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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