# P5- electric circuits

Revision notes with keywords and a summary.

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• Created on: 18-05-12 19:31
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P5- Electric Circuits

Static electricity
When you get out of car, you sometimes get a small electric shock when you touch the metal door ­
and you might hear a little "crack" as a spark jumps off your hand and the car door. This is caused by
static electricity. Electricity…

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Simple circuits
If you break anywhere in the circuit, everything stops.

This suggests that something has to go all around the circuit to make it work. This something is
electric charges. If it was enough for the charges simply to go from the battery to the lamp, the one if…

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At junctions in parallel circuits, the current splits, with some charges flowing through one branch and
the rest flowing through the other branch. Current is the amount of charge passing through a point
every second. So the amounts in the two branches must add up to equal the total amount…

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LDR can be used to measure the brightness of light or to switch another device on or off when the
brightness of light changes. For example, it could be used to switch an outdoor light on in the evening
and off again in the morning.

A thermistor is another device…

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the current is the same but the potential difference is trebled. The power is proportional to
the current.

Power (watts) = Current (amps) x voltage (volts)

The unit of power is the watt (w). One watt is equal to one joule per second. So if you know the
power, it…

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Its length and thickness is chosen so that it melts if the current goes above the value marked on the
fuse. So it is, `the weakest link' in the circuit. It will melt first if the current for any reason gets bigger
than it should be.

An electricity supply
Generators…

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Distributing electricity
An electric current can be generated by moving a magnet into or out of a coil of wire. The moving
magnet could be replaced by an electromagnet. If a coil is wound round an iron core, it becomes
quite a strong magnet when a current flows through it.…

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Summary
Electric charge
Electric charge is a fundamental property of manner.
Charge cannot be created or destroyed. But positive and negative charges can be separated, and
moved from one object to another, for example by rubbing.

Electric current
A working electric circuit always consists of a closed loop of conducting…

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Keywords
Static electricity
Electric charge
Repel
Attract
Positive, negative
Electron
Electric field
Electric current
Electric circuit
Ammeter
In series
In parallel
Voltage
Resistance
Ohm's law
Voltmeter
Potential difference
Power
Kilowatt-hour
Efficiency
Generator
Electromagnetic induction
Alternating current
Direct current
Transformer