Magnetism Flashcards
What is magnetism?
The force of a magnet that attracts or repels an object
How can we see and measure magnetic field?
By scattering tiny filings around the material.
The closer they are, the stronger is the magnetic field.
What way do the field lines flow
From north to south pole
Where is the cause of magnetism from
ATOMS
if a magnet is cut into its smallest form it still possesses the properties. So must be atoms
What does magnetism of a material depend on
Presence of atomic dipoles which arise from electrons spinning and orbitting around the nucleus
Are dipoles arranged
No, random and dont give net magnetism
If an atom is magnetic does it mean the materials made up OF it are
NO
Define Ferro Magnetic
All atoms line their magnetic field - magnetic
Define anti-ferromagnetic
Magnetic fields are in alternating fashion and all cancel out
Define paramagnetic
Random - not magnetic
What is a domain
Areas in magnetic material that may not be magnetic
How to make domains magnetic
If you apply a strong enough magnetic field outside the material it will align all domains and all will become magnetic
What happens when a wire carries a current
A magnetic field is created around it
How do we demonstrate a wire carrying current
Placing a compass next to it,
deflection noticed.
What is done to a conductor in order to make it more magnetic
Wound into a solenoid
Why does a conductor become more magnetic when wound into a solenoid
As with each turn of the wire, it becomes more magnetic and it is reinforced by the next form
How can you increase the strength of a solenoid
We can insert a piece of ferromagnetic material called a core, which becomes materialised
What is an electromagnet
A solenoid with a soft iron core
What does a soft iron core do?
Does not retain its magnetism when switched off, so we have a magnet which can be turned on and off.
Where are electromagnets used?
- Removing foreign bodies patients eyes
- Brakes on XRAY machine
- CT to alter focal spots
How are electromagnetics used in MRI
Spinning charge of hydrogen in the body causes a magnetic field, the movement in the magnetism across the receiver induces a current in coil which is measured.
What is Faradays Law
magnitude of the induced electromotive force is directly proportional to the rate of change of magnetic flux linked with the circuit.
What does size of current induced in conductor depend on
- strength of magnetic field
- speed of magnet movement
- angle of conductor
- number of coil turns
