Electromagnetism Flashcards
(29 cards)
Like poles (two N poles or two S poles)
- Repel
Unlike poles (N and S pole)
- Attract
What is induced magnetism?
- Magnetism created in an unmagnetised magnetic material when placed in a magnetic field
What is a permanent magnet?
- It produces its own magnetic field
What is a solenoid?
- A current carrying coil
Magnetic field line arrows point:
- From North to South
Which are the 4 most common magnetic materials?
- Nickel
- Cobalt
- Iron
- Steel
What is the difference between a magnet and a magnetic material?
- Magnet is already magnetised and produces its own field
- Magnetic material can be magnetised but is not necessarily
Why is steel used rather than iron to make permanent magnets?
- Because it does not lose its magnetism easily
- Magnetically hard
Why is iron used in the core of electromagnets rather than steel?
- Because it does both magnetise and lose its magnetism easily
- magnetically soft
Why do the earth’s poles move around gradually?
- Earth is partly molten inside
North-seeking pole?
- North pole of a magnet
- Attracted to the ‘magnetic north’ of the Earth
- Which is actually a magnetic south pole
South-seeking pole?
- South pole of a magnet
- Attracted to the ‘magnetic south’ of the Earth
- Which is actually a magnetic north pole
Describe the construction of a simple compass
- Small magnet
- Suspended on a point that is free to rotate
What are the 3 things necessary to build an electromagnet?
- Power supply
- Coil of wire
- Soft iron core
What is the shape of a magnetic field about a straight current carrying wire?
- Circles centred on a wire in a plane perpendicular to the wire
What are the three ways to increase the strength of an electromagnet?
- Use a soft iron core
- Increase the number of turns
- Increase the voltage (in order to increase the current)
What is the motor effect?
- If a current-carrying wire is placed in magnetic field, it will experience the force
How dod you increase the size of the force produced by the moto effect?
- Increase current, by increasing potential difference
- Increase magnetic field strength, by using a stronger magnet or moving magnetic poles closer together
- Increase the length of wire in the field, by increase the number of turns on coil
Fleming’s left Hand Rule?
- FBI
- Force, B-lines, Current
How do you work out the direction of magnetic field around a wire?
- Right hand grip method
- Thumb = current direction
- Fingers = magnetic field direction
What is the purpose of an electric motor?
- To transfer energy electrically into the kinetic store of the motor
How does a speaker work?
- Alternating current signal passed into coil
- Coil makes magnet vibrate
- Magnet attached to cone
- Cone vibrates and makes sound
What is induction?
- When a conductor cuts magnetic field lines, a voltage is induced
