19/11/25
Magnetic fields
The only 4 things affected by a magnetic field are:
A permanent magnet
A magnetic material
A wire carrying a current
A moving charged particle
Magnets have 2 poles – N & S.
Like poles repel, unlike attract.
Iron, nickel and cobalt are magnetic.
A magnetic material has domains pointing in different directions.
A magnet has the domains all pointing in 1 direction.
,When drawing field lines:
They should never cross
They should be continuous
Convention dictates they go from North to South.
We represent the magnetic field when going into and out of page as shown:
Terms
Magnetic field lines can be thought of as lines of flux.
The amount of magnetic flux φ is measured in Webers (Wb).
Also useful is the magnetic flux density (B) (AKA magnetic field strength)
which is measured in Tesla’s (T). This tells us how strong the magnetic field
is. It is also measured in Wbm-2 where 1T = 1Wbm-2.
20/11/25
, Electromagnetism
Fleming’s left-hand rule:
Thumb is motion/force
First is field (N to S)
Second is current (+ to -)
Right hand grip rule:
Thumb in direction of current (towards -)
Fingers are field
If we pass an electric current through a wire there is a magnetic field around
the wire.
We can see the direction of the field using the right-hand grip rule:
We can make the magnetic field stronger by making the wire into a coil:
If current is anticlockwise, North pole produced.
If current is clockwise, South pole produced.
Magnetic fields
The only 4 things affected by a magnetic field are:
A permanent magnet
A magnetic material
A wire carrying a current
A moving charged particle
Magnets have 2 poles – N & S.
Like poles repel, unlike attract.
Iron, nickel and cobalt are magnetic.
A magnetic material has domains pointing in different directions.
A magnet has the domains all pointing in 1 direction.
,When drawing field lines:
They should never cross
They should be continuous
Convention dictates they go from North to South.
We represent the magnetic field when going into and out of page as shown:
Terms
Magnetic field lines can be thought of as lines of flux.
The amount of magnetic flux φ is measured in Webers (Wb).
Also useful is the magnetic flux density (B) (AKA magnetic field strength)
which is measured in Tesla’s (T). This tells us how strong the magnetic field
is. It is also measured in Wbm-2 where 1T = 1Wbm-2.
20/11/25
, Electromagnetism
Fleming’s left-hand rule:
Thumb is motion/force
First is field (N to S)
Second is current (+ to -)
Right hand grip rule:
Thumb in direction of current (towards -)
Fingers are field
If we pass an electric current through a wire there is a magnetic field around
the wire.
We can see the direction of the field using the right-hand grip rule:
We can make the magnetic field stronger by making the wire into a coil:
If current is anticlockwise, North pole produced.
If current is clockwise, South pole produced.
