Summary P7 Magnetism and Electromagnetism

P7 Magnetism and Electromagnetism
Permanent and Induced Magnets
Intro
 Magnets have two poles NORTH (red) and SOUTH (blue)
 Same poles repel each other, opposite poles attract
 Magnetic forces are a NON CONTACT FORCE
Magnetic Field
The region around a magnet where it will exert a FORCE on another magnet or on a MAGNETIC
MATERIAL (iron, steel, nickel, cobalt)
 Plotting compass: used to investigate then magnetic field around a
bar magnet
 Magnetic field lines ALWAYS point from north pole to south pole
 Magnetic field is stronger where the field lines are closer together
(the poles of the magnet)
 Magnetic field of the earth
 South pole is at geographical north and vice versa
 This is why compasses point north because they are
attracted to the south pole which is geographical north
 Earth’s magnetic field is due to the core.
Permanent magnets
A magnet which produces its own magnetic field, always has the same north and South Pole
Induced magnets
Induced magnet: a material that becomes a magnet when it is placed inside magnetic field
 Induced magnets are only ever attracted to PERMANENET MAGNETS
 When it is removed from a magnetic field it will be demagnetised

Electromagnetism
Electromagnetism in a circuit
 When a current flows through a conducting wire a magnetic field is produced around
the wire.
 You can use fleming’s right hand rule to find out the direction of the magnetic field in
a wire
 Strength of the magnetic field depends on:
1. Size of current
2. Distance from the wire
Solenoid
 Solenoid produced by wrapping a wire in a cylinder shape lots of times
 Magnetic field of a solenoid looks identical to bar magnet, its STRONG AND UNIFORM
 Adding an iron core increases the strength of the magnetic field of the solenoid, this is an
electromagnet