1. Electromagnets
D. Crowley, 2008

2. Electromagnets
To know how to make, and test the strength of an electromagnet

3. Magnetism Below are the results of a magnetism experiment
Your task is to analyse these results, writing a conclusions for experiments A, B and C…

4. Magnetism Experiment A: - Experiment B: - Experiment C: -
There must be a magnet in the clamp
The paper clip is attracted
The paper clip is made from a magnetic material: iron (+ steel); cobalt or nickel
Experiment B: -
Paper has no effect on the attraction of the paper clip to the magnet, not affecting its magnetic field
Experiment C: -
The sheet of magnetic material affects the magnetic field of the magnet, changing it so the paper clip is no longer attracted

5. Electromagnets
When electricity is passed through a coil of wire, the coil has a magnetic field around it – this is an electromagnet
If the coil of wire is wrapped around a piece of iron, such as an iron nail, the magnetic field gets stronger

6. Electromagnets
A magnetic field is produced when an electric current flows through a coil of wire - this is an electromagnet (a solenoid is a long coil of wire)
Electromagnets strength can be increased via the following: -
Wrapping the coil around an iron core
Adding more turns to the coil
Increasing the current flowing through the coil

7. Electromagnets
The magnetic field around an electromagnet is just the same as the one around a bar magnet
It can, however, be reversed by turning the battery around
Unlike bar magnets, which are permanent magnets, the magnetism of electromagnets can be turned on and off just by closing or opening the switch

8. Electromagnets
Complete the electromagnets worksheet and the two experiments: –
Finding out how many paper clips the electromagnet can hold when the number of coils is increased
Finding out how many paper clips the electromagnet can hold when the current flowing through the wires is increased

9. Electromagnets More turns = stronger electromagnet
More current = stronger electromagnet
Iron core = stronger electromagnet as it increases the magnetic field strength (plus iron is magnetically “soft” so it can be turned on/off (steel is magnetically “hard”, retaining its magnetism (good for permanent magnets))
Insulated wires
Core
Crocodile clips
Connecting wires
Power pack

10. Experiments
Complete the 2 experiments…

11. Experiment 1
Investigate what happens when more turns in the coil are added
More turns = stronger magnetic field = stronger electromagnet

12. Experiment 2
Investigate what happens when more turns in the coil are added
More current = stronger magnetic field = stronger electromagnet