# Electromagnetism

Electromagnetism

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## 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 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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## The motor

(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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## Electromagnetic induction

• 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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## Transformers

• 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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## equations

V= I x R

Transformer

v= voltage N=number of turns S=secondary P=primary

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Hiya, I don't know if it was just me, but the pdf file is unable to load, something about it being damaged and unrepairable? I wasn't sure if the problem was from my end or yours but I thought I'd let you know just incase (:

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