P2 - All About Electricity - Revision Cards in GCSE Physics

Producing and Distributing Electricity

National Grid - network of pylons and cables that covers the country
electricity taken from power stations to homes/industries
aim of power stations - convert a form of energy into electricty
a power station has 3 steps;
- 1. generate steam
- 2. pass steam through turbines, making them turn
- 3. movement allows generator to turn it into electricity
power stations are innefficient, as energy is lost through sound and heat
fossil fuels: advantages - a concentrated source of energy. Disadvantages - causes acid rain and greenhouse gases, it's expensive to get from countries abroad, and it's unrenewable.
biomass: advantages - renewable, carbon neutral process, doesn't require imports of material. Disadvantages - takes time (and space) to grow, you need a lot of material to get enough energy.
nuclear power: advantages - quick, effective. Disadvantages - potentially dangerous.
photocells: advantages - renewable, sturdy, wireless, low maintenance. Disadvantages - doesn't work at night, energy reduced in bad weather.
wind power: advantages - cheap, renewable. Disadvantages - requires wind, looks ugly.

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electromagnetic induction; creating a voltage, and sometimes current, in a wire experiencing a change in magnetic field.
dynamo effect; using electromagnetic induction to turn kinetic energy into electricity.
electromagnetic induction happens when;
- electrical conductor moves through magnetic field
- OR magnetic field moves through electrical conductor
to reverse voltage or current, you need to reverse the direction of movement
increasing the strength of magnet, the number of turns on the coil or the speed of movement will make a bigger voltage and current
generators move coil in magnetic field, and every half turn the current swaps direction
generators produce AC
dynamos on bikes rotate magnet near coil

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to transmit lots of electricity, high voltage/current in needed, but this means more heat energy wasted through cable.
cheaper to increase voltage while keeping current low, as less energy wasted through cable heat.
step-up transmformers increase voltage
step-down transformers make it safe to be used in homes
transformers only work on alternating current (AC)
power stations aren't efficient.
total energy input = useful energy output + waste energy output
efficiency = useful energy output / total energy input

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power measured in watts (W) or kilowatts (kW)
1 watt = 1 joule per second
to work out power of appliance: Power (W) = Voltage (V) x Current (A)
kilowatt-hour (kWh) is amount of energy converted by 1kW appliance
energy supplied (kWh) = power (kW) x time (h)
cost = number of units x price per unit
off-peak electricity is electricity supplied at night
advantages of off-peak electricity:
- cost-effective for company
- cheaper for consumers
disadvantages of off-peak electricity:
- risk of fire in homes
- stop enjoying use of electricity in day

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