Hey guys, here's a whole topic summary for AQA physics magnetism and electromagnets this has some of the coolest
Practicals in it if you wanna make sure that you've covered all of the practicals you can get knowledge checklist
Over in my free version guide or you can get that Amazon
When we have two like poles they're going to repel
But when we have two unlike poles
They're going to attract
Permanent magnet is going to have a magnetic field which goes from north to south
And we can induce a magnet, a temporary magnet, if we place something inside that magnetic field
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 a battery some wire and an iron. Because all an
Electromagnet is, is an iron core with a wire around it connects it up to a current.
You can use this to pick up things like and paper clips 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 Y is wrapped around that iron core
All Fleming's left hand rule. We need to make our left hand in this shape here
so a finger pointing out Thumb up, figured out your first finger is your
Magnetic fields this thing here is a 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 (turn) your hand
Until it fits in the right direction so first is nice and easy my field is going in that direction
My current is going in that direction
So the movement of the force is going upwards this one here
Isn't really 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
Or were 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= Magnetic Flux Density × Current × Length
You'll notice really annoyingly that this is an uppercase I add a lowercase L
Our units for this for force are Newtons
For Magnetic Flux Density, they are Tesla
For current, It is amps and for length
That is meters
While this is called a 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 nearly 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's moving past some north face of the magnet the force is going to be going up
And because once I've been pushed down that other sides being pushed up. It is going to turn around a
Moving coil loudspeaker works by making the diaphragm attached to a quarrel vibrates
While we have a current passing through the coil the force that is generated by the motor effect makes the (half/quantum) wave
Every time the current changes direction the force
reverses direction so the quote is gonna be going back and forwards making the zypher and go back and forward generating the sound waves a
Moving car microphone works the same principle
but in the opposite direction.
Sound causes the diaphragm to vibrate the diaphragm is attached to the coil the
Vibration of the diaphragm moves the coil which is got to cause their coils move backwards and forwards past the magnets
The generator effect is just an extension of Fleming's left hand rule when we have a wire
And we move it's through a magnetic field. We are going to be generating a current
In a transformer we have a soft iron core
We have a wire which is going to be coiling around and you notice through a different number of coils here
we are going to be looking at varying number of coils so that we can vary the
voltage that goes into that comes out of our transformer if we have a step-up
Transformer the secondary voltage is going to be greater than the primary
Voltage so the voltage coming out is very greater than the voltage going in if we have a step-down
transformer the secondary voltage is going to be less than the primary voltage so the
Voltage coming out is going to be less than the voltage going in
When we are looking at transformers calculations we have
voltage in the primary coil ÷ voltage in the secondary coil
Equals the number of turns in the primary coil divided by the number of turns in the secondary coil
our units for this are going to be for voltage that is volts and
Number of turns doesn't have a unit because it's just a number
You need to know that voltage in the secondary coil
Times the current in the secondary coil
Is equal to voltage in the primary coil times the current in the primary coil and
Our units for voltage are volts for current
amps
voltage volts currents
amps
[outro]
[Transcribes by Flowerboi]
