Summary Physics Edexcel IGCSE: Topic 5; Magnetism and Electromagnetism
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Course
Science
Institution
GCSE
Physics Edexcel IGCSE
All content in Topic 5
Everything you need to know about Magnetism and Electromagnetism, with adequate detail.
Notes taken from the CGP Physics guide for this exam board.
Includes extra detail and visual guides.
Magnets and magnetic fields
Magnets produce magnetic fields, and have two poles (North and South)
A magnetic field- a region where magnetic materials experience a force
Magnetic field lines are used to show the size and direction of magnetic fields. They always
point from north to south.
Placing the north and south poles of two permanent bar magnets near each other creates a
uniform field between two magnets.
Compasses and iron fillects align themselves with magnetic fields.
- You can use multiple compases to see the magnetic field lines coming out of magnets.
- You can use iron filings, on top of a piece of paper of a magnet to form the patter of the
magnetic field.
Magnets affect magnetic materials and other magnets.
Like poles repel, and opposite poles attract.
When magnetic materials are brought near a magnet, the material acts as a magnet.
This magnetism has been induced by the original magnet.
The closer the magnet and the magnetic material get, the stronger the induced magnet will be.
Electromagnetism
An electric current in a conductor produced a magnetic field around it.
The larger the electric current, the stronger the magnetic field.
The direction of the magnetic field depends on the direction of the current.
Magnetic field around a straight wire:
A straight, current-carrying wire will have a magnetic field around it.
The field is made up of concentric circles within the wire in the centre.
Magnetic field around a flat, circular coil:
There are concentric ellipses of magnetic field lines around the coil
The magnetic field around a Solenoid:
The magnetic field lines inside a solenoid are strong and uniform.
Outside the coil, the field is like that of a bar magnet; the ends act like the North and South pole.
This is an electromagnet.
A magnetic material is considered ‘soft’ if it loses its induced magnetism quickly, e.g. iron.
It is considered ‘hard’ if it keeps its magnetism permanently, like steel.
Iron is used in transformers because of its ability to magnetise and demagnetise easily.
You can increase the strength of the magnetic field around solenoid by adding a magnetically
soft iron core through the middle of the core.
, The Motor effect
When a current carrying wire is put between magnetic poles, the magnetic fields affect one
another. The result is a force on the wire, which can cause the wire to move. This is called the
motor effect.
This is because the charged particles moving through a magnetic field will experience a force,
as long as they’re not moving parallel to the field lines.
To experience the full force, the wire has to be at 90° to the magnetic field. If the wire runs
along the magnetic field, it wont experience any force at all. At angles in between, it’ll feel some
force.
The force always acts in the same direction relative to the magnetic field of the magnets and the
direction of the current in the wire.
A good way of showing the direction of the force is to apply a current to a set of rails inside a
horseshoe magnet.
A bar is placed on the rails, which completes the circuit, and this generates a force that rolls the
bar along the rails.
The magnitude of the force increases with the strength of the magnetic field.
The force also increases with the amount of current flowing through the conductor.
Reversing the current or the magnetic field also reverses the direction of the force.
Fleming’s left-hand rule
- tells you which way the force acts.
Electric motors and loudspeakers
A simple C.D. Electric motor:
- Uses the motor effect to get
and keep it moving
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