all u need to know on electrical devices for the P1a AQA exam

a fact sheet on P1As AQA electrical devices

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13.3 ­ Why are electrical Devices so useful?
Why is electricity so useful?
We take electricity for granted in our homes and schools. It is very easy to plug in an appliance or
switch on a light. Electricity is clean, and, if used properly, very safe. It can do all sorts of jobs that
other energies can do, and more. It is possible to heat and light with gas. It could theoretically be
possible to use a gas-powered Hoover, but a TV or computer can only work with electricity.
Electricity is used so much in modern life because it's a quick and easy way to transport energy. Just
think how much easier it is to send electricity down a wire than it is to send chemical energy (in
petrol or coal, for example) by road.
Have a look at this kitchen:
You can see a range of appliances that all use electricity, each one doing a different job, all easy to
use.
We can compare the use of different appliances for a particular job.
Energy Transformations in Everyday Appliances
Electricity isn't useful as it is. To make use of the energy carried by it, electrical energy has to be
converted into other forms of energy. For example:
A drill:
Electrical Energy Movement (Kinetic) Energy
A radio:
Electrical Energy Sound Energy
Electrical energy is always converted into other energy, some examples are shown below:
Appliance Useful Energy Other Energy
Drill Kinetic Sound/thermal
Iron Heat
Hoover Movement (kinetic) Sound/thermal
TV Set Sound/Light thermal

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­ Why are electrical Devices so useful?
The power of an appliance
How much does it cost to use an appliance?
When we work out the cost of using an appliance, we pay for the energy that has been used. We
could pay for the number of joules used, but the joule is only a small unit. So we need a bigger unit.
This is called the kilowatt-hour (kWh).…read more

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Question: How much does it cost to watch 4.5 hours of TV which has a power of 300 watts?
Electricity costs 12 p per unit.
13.3 ­ Why are electrical Devices so useful?
How do we get electricity to our homes?
Electrical energy cannot be stored as electricity itself. For example, a battery stores it as chemical
energy. We are constantly using electricity, so it has to be constantly generated.…read more

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Heavy industry 11 000 V
Light Industry 415 V
Homes 230 V…read more

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