# P1 - Electrical Energy Flashcards

What is the useful energy of a hairdryer?

- Kinetic energy from the fan.

- Heat energy from the filament.

What is the wasted energy from a lightbulb?

Heat energy from the filament.

Why are electrical appliances so useful?

They can transfer electrical energy into useful energy quickly.

How can you determine the best appliance for a job?

It should be as efficient as possible.

What is power?

The rate of transfer of energy.

How do you calculate the power of an appliance?

P = E / t

What unit is power measured in?

Watts or Js^-1

How do you calculate power efficiency?

Useful power / input power

What is a kWh?

The energy transferred to a 1kW appliance in an hour.

How is energy transfer calculated?

E = P x t

How is an electricity bill calculated?

Number of kWh x cost per kWh

What costs have to be considered with energy saving appliances?

- Capital costs
- Running costs
- Environmental costs
- other costs such as interest

What is cost effectiveness?

Getting the best value for money

Give two advantages of loft insulation

- Relatively cheap

- Quick payback time

Give three advantages of an LED bulb

- Low power
- High efficiency
- Long lifespan