T6: magnetism
Cards (19)
- like charges repel
- opposing charges attract
- permanent magnets:
- magnetically hard materials = steel
- retain magnetism
- temporary magnets:
- magnetically soft materials = iron
- lose magnetism when no longer in magnetic field
- used for electromagnets
- magnetic field = region of space where magnetism can be detected
- field lines always point north to south
- magnetic materials near the pole of a strong or permanent magnet = become magnetised = temporary magnet
- uniform magnetic field lines are straight parallel lines - evenly spaced
- an electric current in a conductor creates a magnetic field around wire
- left hand rule: thumb = motion, forefinger = field lines, second finger = current
- motor (why a force):
- current flows in wire
- magnetic field
- interacts with permanent magnetic field
- produced force
- split-ring commutator changes direction of forces every half turn in a motor
- loud speaker (why a force):
- AC current = passes through coils in speaker
- changes direction and magnitude constantly
- creates magnetic field
- interacts with magnetic field of coil
- constant changing force = coils vibrate = produce sound waves
- increasing magnitude of current or size of magnet used = increase force on wire
- changing direction of current or reverse the poles = change direction of force
- voltage is induced in a conductor or coil when moving through magnetic field - strength depends on magnetic field strength
- generation of electricity (rotating coil):
- coil rotated in a magnetic field
- coil cuts field lines as turns
- induces voltage in coil
- can be connected to a circuit
- energy converted from kinetic to electrical
- increase size of induced voltage by:
- stronger magnet
- more turns in coil
- spinning coil faster
- generation of electricity (rotating magnet):
- magnet rotated within a coil
- coil cuts the constantly changing magnetic field lines from magnet
- induces voltage in coil
- connect to a circuit
- convert kinetic energy to electrical energy