Physics Notes – Magnetism
Magnets
General rules
Magnets have two poles, the place where the magnetic field is strongest, most magnets have a north and a
south pole
Like poles repel, opposite poles attract
Types of magnet
Permanent Magnets - Always magnetic, always have poles
Induced Magnet – A piece of magnetic material in a magnetic field that acts as a magnet
Induced magnets can be made into temporary magnets by passing a permanent magnet over to align
the domains
Electrons moving produce a magnetic field, but if they don’t move in the same direction, the fields cancel
out. In magnets they move/spin in the same direction.
Magnetic materials are iron, nickel and cobalt and any alloys containing them
In magnets the domains are aligned
- NB – only the edge of the magnet is the pole.
Magnetic Fields
Definition
A magnetic field is a region of space in which a
magnetic object (or another magnet) will feel a force.
Field Lines
point from North to South
Strength decreases with distance from the magnet
Never Terminate
Magnetic field lines show:
Strength (the spacing of the field lines)
Direction
Where the field is
, A plotting compass can be used to show the magnetic field of a bar magnet. These are the steps:
1. Put compass at one pole of magnet
2. Record direction of N.Pole
3. Put compass on your mark (top to tail with previous position)
4. Continue process until you get to the other pole
5. Join the dots with arrows showing the direction of the South Pole.
6. Repeat with another line
NB – the magnetic field lines can never cross
Earth’s Magnetic Field:
It makes the Earth habitable as it protects it from some radiation from the sun
Uniform magnetic fields
To make a uniform magnetic field:
Place 2 bar magnets
With opposite poles facing each other
Close together
Test to see if something is magnetic:
Take a magnet,
place the object within its magnetic field,
observe it and see if it is attracted.
If so, it is magnetic.
Test to see if something is a magnet:
Take a known magnet, place the object within its magnetic field.
If it attracts then it could either be a magnet or just magnetic.
Repeat using the opposite pole of the magnet.
If it repels then it is a magnet.
Solenoids (not needed)
Magnets
General rules
Magnets have two poles, the place where the magnetic field is strongest, most magnets have a north and a
south pole
Like poles repel, opposite poles attract
Types of magnet
Permanent Magnets - Always magnetic, always have poles
Induced Magnet – A piece of magnetic material in a magnetic field that acts as a magnet
Induced magnets can be made into temporary magnets by passing a permanent magnet over to align
the domains
Electrons moving produce a magnetic field, but if they don’t move in the same direction, the fields cancel
out. In magnets they move/spin in the same direction.
Magnetic materials are iron, nickel and cobalt and any alloys containing them
In magnets the domains are aligned
- NB – only the edge of the magnet is the pole.
Magnetic Fields
Definition
A magnetic field is a region of space in which a
magnetic object (or another magnet) will feel a force.
Field Lines
point from North to South
Strength decreases with distance from the magnet
Never Terminate
Magnetic field lines show:
Strength (the spacing of the field lines)
Direction
Where the field is
, A plotting compass can be used to show the magnetic field of a bar magnet. These are the steps:
1. Put compass at one pole of magnet
2. Record direction of N.Pole
3. Put compass on your mark (top to tail with previous position)
4. Continue process until you get to the other pole
5. Join the dots with arrows showing the direction of the South Pole.
6. Repeat with another line
NB – the magnetic field lines can never cross
Earth’s Magnetic Field:
It makes the Earth habitable as it protects it from some radiation from the sun
Uniform magnetic fields
To make a uniform magnetic field:
Place 2 bar magnets
With opposite poles facing each other
Close together
Test to see if something is magnetic:
Take a magnet,
place the object within its magnetic field,
observe it and see if it is attracted.
If so, it is magnetic.
Test to see if something is a magnet:
Take a known magnet, place the object within its magnetic field.
If it attracts then it could either be a magnet or just magnetic.
Repeat using the opposite pole of the magnet.
If it repels then it is a magnet.
Solenoids (not needed)
