Hey guys this year because all the way she needs to know about magnetism your Edexcel physics
When we have two light poles they're going to repel
but when we have two unlike poles
they're going to attract.
A permanent magnet is going to have a magnetic fields which goes from north to south and
we can induce a magnet a temporary magnet if we place something inside that magnetic fields
Magnetic materials are going to be metals and
That is going to include iron
Nickel and
Cobalt
You can easily make an electromagnet at home all you need is battery some wire and an iron now because all an
Electromagnet is is an iron core with a wire around it connected up to a current?
You can use this to pick up things like an paperclips or iron filings
When a current is passed through the wire it creates a magnetic field around the wire and this in turn
strongly magnetizes the iron bar thus creating our electromagnets
If you want to change the strength of an electromagnet you can do two things you can change the current
Or you change the number of turns or the number of coils that the Y times the wire is wrapped around that iron core
Or Fleming's left hand rule. We need to make our left hand in this shape here
So a finger pointing out sum up finger out your first finger is your magnetic feels
This thing here is the current and then your thumb is the movement of the force?
And what you need to do when you have an exam question is literally you can taught your hand until
It fits in the right direction so first it's nice and easy my field
Is going in that direction my colony is going in that direction?
So the movement of the force is going upwards this one
Here is more complicated this finger needs to be pointing in that direction
My current needs to be going down and then my thumb is going into the page
We can change the size of a force by changing the current
By changing the strength of the magnets
Over changing the angle between the wire and the magnetic field lines
The greatest force is when the Y is perpendicular
With magnetic field lines and the force is going to be zero if the wire and the field lines are parallel
Magnetic flux density is the amount of magnetic flux in a certain area and the equation that we use for this is force
equals
magnetic flux density
Times current
Times length you'll notice really annoyingly that this is an uppercase. I and a lowercase L
Are units for this for force on Newtons for magnetic flux density
They are Tesla for current. It is amps and for length
That is meters
While these colder simple electric motor is actually quite sort of physics going on here and for this we really need to use our Fleming's
Left hand rule so our magnetic field is going from north to south
like this
Our current is moving actually in two different directions
On this side, it's moving in this direction
And on the other side is moving in this direction
So what we are going to have is that when the?
Wire is being passed south via the magnet the force is going to be going down
And when it smoothly past the north face of the magnet the force is going to be going up
And because one side being pushed down and that other side being pushed up. It is going to turn around a
Moving coil loudspeaker works by making a diaphragm attached to a coil of our brains well
We have a current passing through the coil the force that is generated by the motor effect makes the quantum wave
Every time the current changes direction the force
Reverses direction so the coil is really going back and forwards making the zypher and go back and forward generating the sound waves
A moving cool microphone works the same principle, but in the opposite direction
Sound causes the diaphragm to vibrate the diaphragm is attached to the coil though
Vibrations diaphragm moves the coil which is going to cause their coil to move backwards and forwards past the magnets