Magnetism and Electromagnetism Flashcards
how many poles do magnets have? and what are they?
they have two poles, north and south
what is a magnetic field?
where magnetic materials experiences a force
what are magnetic field lines used for?
to show the size and direction of magnetic fields
where do magnetic field lines usually point to?
they always point from north to south
what happens if you place the north and south poles of two permanent bar magnets near each other?
it creates a uniform field between the two magnets
describe what a uniform field looks like
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describe what magnetic field lines looks like
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what do magnetics produce?
a magnetic field
how can you see magnetic field patterns?
by using a compass
why can you see magnetic field patterns with compasses and iron fillings?
because they align themselves with magnetic fields
how can you see magnetic fields coming out of a bar of magnets?
by using multiple compasses
describe how magnetic fields look like coming out of a magnet bar
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what do magnets affect?
they affect magnetic materials and other magnets
what do similar poles do with each other?
they repel each other
what do opposite poles do with each other?
they attract each other
describe how poles repealing each other looks like
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describe how poles attracting each other looks like
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what do poles attract?
they attract magnetic materials (that aren’t magnets)
what happens when magnetic materials are brought near to a magnet’s magnetic field?
that materials acts as a magnet
why does a magnetic material acts as a magnet when it is brought close to a magnet?
because this magnetism has been induced by the original magnet
what happens with the closer the magnet and the magnetic material get with each other?
the stronger the induced magnetism will be
what happens when an electric current flows?
it produces a magnetic field
what does an electric current in a conductor produce?
it produces a magnetic field around it
what does the direction of the magnetic field depend on?
on the direction of the current
how will the size of the electric current affect the magnetic field?
if the electric current is larger the magnetic field will be stronger
if the electric current is smaller the magnetic field will be weaker
what causes a magnetic material be considered as soft?
if it loses its induced magnetism quickly
what causes a magnetic material be considered as hard?
if it keeps its induced magnetism permanently
what is an example of a soft magnetic material?
iron
what is an example of a hard magnetic material?
steel
how can you increase the strength of a magnetic field around a solenoid?
by adding a magnetically “soft” iron core through the middle of the coil
what is the motor effect?
it is when a current-carrying wire is put between magnetic poles, the two magnetic fields affect one another. The result is a force on the wire. This can cause the wire to move
what do electric motors use to get them moving?
the motor effect
what are 4 factors that will speed up an electric motor?
- more current
- more turns on the coil
- stronger magnetic field
- a soft iron core in the coil
how do loudspeakers work?
using the motor effect
describe with detail how a speaker works
there are 3 steps
1) the a.c. electrical signals from an amplifier are fed to a coil of wire in the speaker, which is wrapped around the base of a cone
2) the coil is surrounded by a permanent magnet, so the a.c. signals cause a force on the coil and make it move back and fourth
3) these movements make the cone vibrate and this creates sound
how is the Fleming’s left hand rule?
using your left hand, point your First finger in the direction of the Field and your seCond finger in the direction of the Current. Your thuMb will then point in the direction of the force (Motion)
what is electromagnetic induction?
the creation of a voltage (and maybe current) in a wire which is experiencing a change in magnetic field
what is the dynamo effect?
when electromagnetic induction is used to generate electricity using energy from kinetic energy stores
what are two different situation where you get electromagnetic induction?
a) when an electrical conductor moves through a magnetic field
b) when the magnetic field through an electrical conductor changes
what do you need to do to get a bigger voltage?
you need to increase…
- the strength of the magnet
- the number of turns on the coil
- the speed of movement
how can you test the magnitude and direction of the induced current?
you can test it by connecting an ammeter to a conductor and moving the conductor through a magnetic field (or moving a magnetic through the conductor)
how does a generator work?
there are 6 points that need to be made
1) generators rotate a coil in the magnetic field
2) their construction is pretty much like a motor
3) as the coil spins, a current is induced in the coil. This current changes direction every half turn
4) instead of a split-ring commutator, a.c. generators have slip rings and brushes so the contact s don’t swap every half turn
5) this means they produce a.c. voltage. The faster revolutions produce not only peaks but higher overall voltage too
6) power stations use a.c. generators to produce electricity, they get the energy needed to turn the coil or magnetic field in different ways
