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
