P1 3 Electrical Power + Energy Flashcards Preview

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Flashcards in P1 3 Electrical Power + Energy Deck (13)
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Why should an electrical appliance waste as little energy as possible?

An electrical appliance is designed for a particular purpose so a small amount of energy should be wasted.


What are some uses of electrical appliances?

Electrical appliance uses can include: heating, lighting, making objects move by using an electric motor and creating sound and visual images.


What is power?

Power is the rate of transfer of energy.



The more powerful an appliance ...

... The faster the rate at which it transfers energy.


What is the formula for calculating power?

Power = Energy / Time.

Power in watts W.
Energy in joules J.
Time in seconds s.


What is the efficiency of a device?

The efficiency of a device is the useful power out /
The total power in.

x 100 for a percentage.


What is a kilowatt-hour?

The energy supplied to 1 kW appliance in 1 hour.


What does the energy supplied to an appliance depend on?

• How long it's used for.
• The power supplied to it.


How to work out the total cost:

Total cost = number of kWh x cost per kWh.


What is a kilowatt-hour?

A unit of energy.


What does cost effectiveness mean?

Cost effectiveness means getting the best value for money.


What are all the costs of an appliance?

• Capital costs- buying and installing the equipment.
• Running costs- fuel and maintenance.
• Environmental costs- removal of old equipment and carbon tax.
• Other costs such as loan interests.


What is the payback time?

The payback time is the time taken for something to produce savings to match how much it cost.