P1.3 - The Usefulness of Electrical Appliances Flashcards
What can everyday electrical devices do?
Everyday electrical devices can bring about many different types of energy transformation.
What does the amount of energy transferred by an appliance depend on?
The amount of energy transferred by an appliance depends on its power and the amount of time that the appliance is switched on for.
What is an appliance’s power?
How fast the appliance can transfer energy.
What is the formula for energy transfer?
E = P * T or Energy = Power * Time
Energy is measured in joules (J) or kilo-joules (kJ).
Power is measured in watts (W) or kilowatts (kW).
Time is measured in seconds (s) or hours (h).
1 watt of energy is…
1 watt transfers 1 joule of electrical energy to other forms of energy every second.
What is a kilowatt hour?
A kilowatt-hour is the amount of electrical energy used by a 1kW appliance left on for an hour.
Why is a kilowatt-hour used?
It is used because it is a better unit than the joule.
What is the equation for cost?
Cost = Units * Price (per unit)
What are usually the units for electricity meters?
The units are usually in kWh.
How do you find an electricity meter reading?
Subtract the smaller reading from the larger one.
What things are there to consider when choosing appliances?
Things to consider when choosing appliances include the cost of running the appliance and whether it is more cost-effective than another.
When are clockwork radios and battery operated devices useful?
Clockwork/battery operated devices are useful if there is no mains supply available.
How do clockwork radios work?
Clockwork radios store elastic potential energy in a spring when wound up, and the elastic potential energy is slowly released to power the radio.
Evaluate battery powered radios.
Battery powered radios are useful if the battery supply can be replenished.
If the batteries are in short supply then it is expensive to replace them. They also contribute negatively to the environment thanks to the batteries.
How does electricity improve the standard of living?
Electricity can:
- Transfer electrical energy into other forms of energy - it can be used to light areas at night.
- Refrigerate items like food to slow down the growth of bacteria, keeping food fresh.
- Improve public health by keeping people alive via heart monitors, x-rays, etc
- Coordinate the sharing of information by powering the devices behind the internet.
