Electromagnetism and Magnetism Flashcards
What are the magnetic materials?
Iron, steel, nickel, cobalt
What does it mean if the lines are closer together?
The magnetic field will be stronger
where is the magnetic field the strongest?
At the poles
what do permanent magnets do?
produce their own magnetic field
what do induced magnets do?
become a magnet when they are placed in a magnetic field
What makes the magnetic field stronger?
larger current
closer to the wire you are
solenoid
How can you increase strength of a solenoid?
add an iron core, that will become induced
why are electromagnets useful?
you can switch then on and off to creating a varying force
What are uses of electromagnets?
in cranes to attract and pick up things made of magnetic material
within other circuits to act as switches
what is the motor effect?
a wire is put between magnetic poles, magnetic field around wire interacts with magnetic field its been placed in. The magnet and the conductor exert a force on eachother and the wire begins to move.
what happens when the wire runs parallel to the magnetic field?
it will experience no force
what does the force acting on a conductor depend on?
magnetic flux density - shows strength
current
length of conductor in magnetic field
what does the split ring commutator do?
swaps the contacts every half turn to keep the motor rotating in same direction
How can the direction of motor be reversed?
reversing the current or reversing the field (swapping magnetic poles over)
How do loud speakers and headphones work?
alternating current sent through the coil of wire
coile surrounds one pole of perm magnet
surrounded by other pole so current causes force on coil
current reversed
force acts in opposite direction
cone moves in opposite direction
variations of current make cone vibrate to cause pressure then sound waves
what is the generator effect?
induction of potential difference in a wire which is moving relative to magnetic field, or change in magnetic field
How can you create a potential difference and current in conductor for the generator effect?
moving a magnet in a coil of wire or moving the wire in a magnetic field.
what does a change in magnetic field do?
induces a current in a wire
Why does the magnetic field created in an induced current acts against the change?
to return things to the way they were, the induced current always opposes the change that made it
How do you increased induced potential difference?
increase speed of movement, cutting more magnetic field lines
increase the strength of the magnetic field
How do generators produce an alternating potential difference?
they have slip rings and brushes so the contacts dont swap every half turn
what do dynamos do?
split-ring commutators to swap connection every half turn to keep current flowing in same direction
How do microphones work?
sound waves hit a flexible diaphrgam attached to a coil of wire wrapped around a magnet
coil moves in magnetic field
generates current
movement of coil depends on property of sound waves
what do transformers look like?
they have 2 coils of wire, primary and secondary, joined with an iron core.
what happens if the second coil of a transformer is a complete circuit?
causes a current to be induced
