P3: Magnetisum Flashcards
What do the arrows represent on field diagrams?
The arrows on the field lines always point from the North Pole of the magnet to the South Pole.
What happens when a current flows through a wire? How is the field made up?
A magnetic field is created around the wire. The field is made up of concentric circles with the wire in the centre (the right hand thumb rule shows which way the magnetic field goes)
What is the magnetic field structure inside and outside a coil of wire?
Inside- Strong and uniform
Outside- one like a bar magnet
What happens when you stop the electric current? What is it called when this can be switched on and off?
The magnetic field disappears
Electromagnet
How can you increase the strength of the magnetic field round a coil of wire (solenoid)?
Why does this work?
Adding a magnetically “soft” iron core through the middle of the coil.
A magnetically soft material magnetises and demagnetises very easily. So, as soon as you turn off the current the magnetic field disappears- the iron doesn’t stay magnetised. This is what makes it useful for something that needs to be able to switch it’s magnetism on and off
Give examples of an electromagnet?
Cranes- can pick up and drop iron and steel. If an ordinary magnet was used instead it would pick it up but then not let go.
What happens when u put the wire into a magnetic field?
What is this called?
You have two magnetic fields combining which puts a force on the wire.
Motor effect
How would the force of the wire increase?
Increasing the current of the magnetic field.
What happens if the direction of the current or magnetic field is reversed?
Direction of the force is reversed too. You can always predict which way the force will act use in Fleming’s left hand rule. You
How do u experience full force on the wire?
Wire has to be 90° to the magnetic field.
What happens if the wire runs parallel to the magnetic field?
It won’t experience a force at all
What is Fleming’s left hand rule?
1) Point your First finger in the direction of the Field.
2) Point your seCond finger in the direction of the Current.
3) Your thuMb will point in the direction of the force (Motion).
What is the simple electric motor?
1) Force acting on the two side arms of the coil of wire.
2) Forces are the usual forces acting on any current in a magnetic field.
3) Coil is on a spindle, and the forced act one up and one down, it rotates.
4) Split-ring commutator is a clever way of “swapping the contacts every half turn to keep the motor rotating in the same direction”
5) The direction of the motor can be reversed by either swapping the polarity of the DC or swapping the magnetic poles.
6) Speed it up by: more current; stronger magnetic field.
Where are electric motors used?
CD players, food mixers, printers, fans, drills
Fans- link the coil to the axle, and the axle spins.
What is electromagnetic induction?
The creation of a different potential difference across a conductor which is experiencing a change in magnetic field.
