# P1a Complete Revision in 10 pages

This is a brief summary in 10 pages of the whole topic  known as  P1a this is just the basic of the topic.  It is advisable that you may need to get some sort of practice question to make sure you know the key  calculations in depth and details. By Chantel Williams .... I hope this helps .. leave comments for improvements .

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• Created by: chantel
• Created on: 21-07-11 15:14

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P1a Revision You're in charge
Quick basic ks3 knowledge on Some standard symbols are used to represent a
circuit.
An ammeter measures the current.
The voltmeter measure the potential difference.
The cell provided energy to the flow of electrons.
A collection of cells is a battery
A diode allows current to flow in one direction.
The two types of circuits are series and parallel.
In a series circuit if you put more lamps the lamps will be dimmer than
before. If a lamp breaks or a component is disconnected the circuit is
broken and all components stop working it uses less wiring than parallel.
In a parallel circuit if a lamp breaks or disconnected from one parallel
wire components on different branches keep working. Stay bright if
more Lamps are added. This is why our homes wired up with parallel
circuits.
Current Voltage
Measured in amps, A volts, V
ammeter in voltmeter in
Measured with
series parallel
Circuit symbol of
measuring devise

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Voltage is measured across a lamp; the more cells the bigger the voltage.
In a series circuit you'll get the same reading of current, the more cells the
more current.
Producing Electricity
There are two types of current Ac and Dc. Direct and alternating current.
Direct current flows in one direction batteries and solar panels supply d.c
current.
If a current constantly changes direction it is an alternating current. Mains

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Increasing induced current
Move the magnet faster
Increase the turns of coil -
Use a stronger magnet -
Increase the area of the coil
Generators induce current by spinning a coil of wire inside a magnetic field or
a magnet inside a coil of wire. As this happens the potential different is
produced at the end of the coil that allows the current to flow.…read more

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More lamps in a series circuit the more resistance this means less current
will flow. A Variable resistor are used in dimmer switches or to adjust
volume of a cd player.
Ohms law : Current flowing through a resistors
is directly proportional to the voltage across the resistor.
But a filament Lamp does not follow this.
The resistance of a filament lamp increases as
the temperature of its filament increases.…read more

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Remember: The resistance of a resistor increases when the temperature is
increased.
Resistance of a Thermistor stays the same when the light level is increased
Ability for battery to supply energy is called capacity, this is measured in amp
hours.
Non rechargeable batteries(Dry cells) output gradually fall and once all
reactants are used up batteries go flat.
Rechargeable batteries: Contain reactants that can be used again by passing

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You're in charge
Fossil Fuels for power stations
The three main fossil fuels are, coal, oil ,natural gas , these were formed from
the remains of living organism millions of years ago.
The wind is produced by giant convection currents in the driven by the heat
energy from the sun .This means that the kinetic energy in the wind is renewable as long as the heat
energy in the sun exists .…read more

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Water energy; water energy has wave machines that use kinetic energy to drive generators
Tidal Barrage ­ A barrier built over the river estuary .The barrage contains electric generators which
are driven by the waters rushing through the tubes in a barrage. This uses moving kenetic energy.
Hydroelectric power (HEP)- Uses kinetic energy in the moving water. Water comes from
behind a dam built across a river valley.…read more

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Disadvantage: Expensive and inefficient, only produce hot water in sunny
climates but cooler areas may need a boiler. Cannot produce warm water at
night.
Mains electricity
Water is turned into steam in the boilers
The steam drives the turbines
The turbines spin the generators, which produce the electricity
The electricity goes to the transformers to produce the correct voltage
Transformers changes the voltage of alternating current.…read more

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In the diagram you can remember this as, blue goes left, brown goes right and
striped goes to the top.
Fuses break if an appliance uses too much current, if the current going
through the fuse is too great the wire heats up and melts then breaks the circuit. Fuses in plugs have
ratings, the fuse is rated at a slightly higher current than the device needs. Most common 3a, 5a,
13A.If the device works at 3a use a 5a fuse.…read more

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The cost of electricity
An electric motor can be built by using a coil of wire that is used to rotate two
opposite magnetic poles
. Direction of the current is reversed every half turn otherwise it will come to an halt.
This is done using a split ring or a communicator.
The amount of electrical charge that flows in a circuit depends on the current flow
and how long it flows for.
Energy is never destroyed but becomes wasteful and not useful to us.…read more