Physics - Magnetic Stuff

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Electric fields travel from __ pole to __ pole
north to south
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field lines represent direction of...
magnetic field (force experienced)
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field lines also show strength. the magnet is stronger then the lines are... (closer/further apart?)
closer
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magnetic fields can be produced by a current in a conductor. give an example of this....
current flowing through conductive wire, creating magnetic field
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the magentic field forms ___ly (in circles) around wire
radially
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the magnetic field is ____ (perpendicular/parallel?) to wire
perpendicular (90 degrees)
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changing current direction will change the ___ direction
magnetic field
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when a current increases, the magnetic field...
becomes more dense to indicate a stronger force
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a permanent magnet always has...
magnetic field
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an induced magnet is a...
magnetic material that becomes magnet in magnetic field
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give examples of a magnetic material
iron, steal, cobalt, nickel
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the earth has a magnetic field due to....
it's core
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we can prove there's a magnetic field around a wire with a....
compass
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if the number of loops in a wire (number of coils) increases, the ___ also increases
strength of magnetic field
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what's can we place in the solenoid (the looped wire) to increase the current?
iron. this is called an iron core
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a solenoid with an iron core is called an...
electromagnet
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why are electromagnets useful?
we can change strength of magnetic field by changing current, and er can turn them on/off
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why are high voltage circuits dangerous to turn off/on?
can get sparking, risk of electrocution
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so to turn circuits like this off, we use a...
relay - containing two seperate circuits
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the low-voltage circuit contains an e___, and is safe to turn on/off
electromagnet
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on the high voltage circuit, switch is replaced with....
two metal contacts, one connected to a spring which keeps contacts apart. there's also an iron block next to the spring
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low voltage circuit is switched on so current runs around circuit so there's a magnetic field around electromagnet. how does thi turn the high voltage circuit on?
magnetic field attracts the iron block so the two contacts close, switching on the high-voltage circuit
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doorbells also use an electromagnet. describe how.
switch is closed when buzzer's pressed, causing current to flow through circuit, producing MF from electromagnet, attracting iron contact, causing clapper to hit bell while breaking circuit so there's no longer current so iron springs back
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what is the motor effect?
when a wire with current in is placed in a magnetic field (between two magnets). the MF between wire interacts with MF between magnets so the wire experiences a force, making it move
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the force depends on three things. magnetic flux density, current and...
length
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how can we calculate the force?
force = magnetic flux density (strength of MF) x current x length
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if the conductor (wire) is parallel to MF, would it still experience a force?
no
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if i loop of wire carries a current, it will be running in opposite directions on either side of loop. true?
yes
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so if the wire is placed in MF, what happens regarding forces?
they'll be force acting on both sides (e.g. upwards and downwards)
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we now have a m__ on each side
moment
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this will cause the wire to r__
rotate
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the loop will stop rotating at __ degrees
90
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why is this?
if loop moves past 90 degrees, the direction of the current means the two forces act opposite each other (e.g one acts downwards while the other acts upwards), pulling loop back to 90 degrees
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how can we resolve this, and get the loop to move past 90?
switch direction of current
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this can be done using a...
split-ring commutator (split metal ring)
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Other cards in this set

Card 2

Front

field lines represent direction of...

Back

magnetic field (force experienced)

Card 3

Front

field lines also show strength. the magnet is stronger then the lines are... (closer/further apart?)

Back

Preview of the front of card 3

Card 4

Front

magnetic fields can be produced by a current in a conductor. give an example of this....

Back

Preview of the front of card 4

Card 5

Front

the magentic field forms ___ly (in circles) around wire

Back

Preview of the front of card 5
View more cards

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