Magnetism and Electromagnetism Flashcards
What is a magnet?
any material or object that produces a magnetic field
What direction do field lines go in?
north to south
How do field lines show field strength?
denser lines show a stronger field
What are the 2 types of magnets?
permanent, induced
What is the difference between a magnet and a magnetic material?
magnet actually produces a magnetic field
magnetic material can be influenced by magnetic field and has potential to become a magnet
What are the 3 main magnetic element?
nickel cobalt iron (+ steel)
What is the difference between an induced and a permanent magnet?
permanent always produce their own magnetic field
induced have a magnetic field temporarily
How are induced magnets created?
when magnetic material - that isn’t magnetised - gets put into the magnetic field of a permanent magnet. This causes it to develop its own north and south pole.
True or False: An induced magnet will always be attracted to the permanent magnet.
true
What is magnetically soft or hard?
magnetically soft materials lose their magnetism fairly quickly. (e.g. iron)
magnetically hard materials lose their magnetism much more slowly. (e.g steel)
what is electromagnetism?
the phenomenon in which electric currents produce their own magnetic fields
What is the right hand rule?
a way of showing the direction of the magnetic field in a wire.
your thumb is the direction of current and the direction your fingers wrap around is the direction of the magnetic field
What is a solenoid?
a magnet created by passing current through a coil of wire
what are 4 ways to increase an electromagnet’s strength?
increase current
increase number of coils
decrease the length of coils (denser coils)
Add an iron core to the inside of the solenoid
What is the motor effect?
when a current carrying wire is placed within a magnetic field, the two magnetic fields will interact and the wire will experience a force.
What is Fleming’s left hand rule?
index finger straight, showing magnetic field
middle finger perpendicular, showing current
thumb point up, showing force
What is the equation to work out the strength of the force in the motor effect?
force = magnetic flux density * current * length of wire (m)
What are the units of magnetic flux density?
tesla
How can you ensure that the wire experiences the full force in the motor effect?
make sure the wire is perpendicular to the magnetic field
What does a split ring commutator do?
swaps the positive and negative connections every half turn, which swaps the direction of the current
Why is a split ring commutator used?
to swap the current every half turn and keep the wire rotating in the same direction.
What would happen to the motor if a split ring commutator was not used?
the wire would turn 180 then turn back and keep oscillating till eventually it stops vertically.
How can you increase speed of rotations in a motor?
increase current
add more turns to the coil
increase magnetic field strength
What is the generator effect?
when you move a wire through a magnetic field, a potential difference will be induced in the wire
what is needed to generate current in the wire in the generator effect?
a complete circuit
How could you change the size of the p.d. induced in the generator effect?
Change strength of magnetic field
move wire or magnets faster
shape the wire into a coil and increase the turns to get a bigger p.d.
Why does the direction of the current repeatedly change in the generator effect?
when the wire moves in one direction a current is produced, but when its stopped and moved back, it generates an opposite current. As it keeps oscillating, alternating current is produced
Will a wire moving parallel or moving perpendicular to the magnetic field generate a p.d.?
perpendicular
