Using electromagets
I can describe how electromagnets are used in cranes, locks, bells and motors.
- Year 9
Using electromagets
I can describe how electromagnets are used in cranes, locks, bells and motors.
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.
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.
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
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.An object that always behaves as a magnet is called a __________ magnet.
Q2.Which of the following objects would be attracted to an electromagnet?
Q3.Which of the following statements explain why soft iron is usually used for the core of an electromagnet?
Q4.Which of the following is a definition of a complete circuit?
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?
Q6.A pupil experiments with a bar magnet and an electromagnet. Which of the following statements are correct?
Assessment exit quiz
6 Questions
Q1.An electromagnet that loses its magnetism when current stops flowing can also be called a __________ magnet.
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?
Q3.Which of the following is the purpose of the springs attached to the bolt of the electromagnetic door lock shown?
Q4.The diagram shows an electric door lock. Which of the following statements are correct?
Q5.The diagram shows an electric bell. Which of the following happen as the switch is pressed?
