The motor effect
- whn a current passes through a wire in a magnetic field a force may be exerted on it.
- this is know as the motor effect
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Changing the force
The force can be effected by:
- increasing the current
- using a stronger magnet
- both increase force
- changing the angle between the wire and field
- greater when wire is perpendicular to the field
- zero when they are parallel
- the direction of the force is always at right angles to the wire and the field.
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The left hand rule
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The electric motor
- uses the same priciples as the motor
- we control the speed of the motor by changing the current
- we can reverse the direction of the motor by reversing the direction of the current.
- the coil spins because:
- a force acts on both sides of the coil in
- the current goes in both directions due to the coil of the wire
- the split rings alow it to spin in one direction, as it means the direction of the current changes every 1/2 a turn.
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(you don't need to know what a torque is, it's a good picture though)
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The Loud speaker
- a Loud speaker is a coil that vibrates a diaphragm when an AC is passed through it.
- the motor effect causes the coil to move
- because it's an AC it goes backward and forward causing it to vibrate.
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- Opposite of a motor- a generator
- it has coil moving in a magnetic field causing a current to start up.
- they always create AC.
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- A power station produces 25000v AC current,a house only wants 230v,on the national grid the voltage is 132000v
To change between we have transformers
- an iron core has two coils wrapped around it when one coil has a current passing through it induses a current in the second
- the core DOES NOT CONDUCT ELECTRICITY.
- they only work for AC current.
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The national Grid
- the higher the grid P.D. the greater the effiecieny of transfering electricity power through the grid.
- this is due to the heat loss of a high current
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V= I x R
v= voltage N=number of turns S=secondary P=primary
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