Download Combustion Equation

Electromagnets
D. Crowley, 2008
Electromagnets
To know how to make, and test the strength of an electromagnet
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…
Magnetism
• Experiment A: – 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
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
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
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
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
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
Experiments
• Complete the 2 experiments…
Experiment 1
• Investigate what happens when more turns in the coil are added
• More turns = stronger magnetic field = stronger electromagnet
Experiment 2
• Investigate what happens when more turns in the coil are added
• More current = stronger magnetic field = stronger electromagnet