Electrical Appliances, Energy and Efficiency Flashcards
How do you calculate efficiency?
Useful power out / total power in
In what form should efficiency be given?
As a decimal or percentage
Why can’t wasted heat energy be used again?
When it is transferred to cooler surroundings it warms them up and becomes less concentrated (dissipates)
What are heat exchangers?
Devices that reduce the amount of heat energy that is lost by pumping a cold fluid through the escaping heat
What does kWh mean?
Kilowatt-hour - the amount of electrical energy used by a 1kW appliances left on for 1 hour
How do you find the number of units used?
Power (kW) * time (hours)
How do you find the cost of electricity?
Units * price per unit
A 60W lightbulb is left on for 30 minutes at the price of 14p per unit. What is the cost?
- 06kW * 0.5 hours = 0.03 units
0. 03 units * £0.14 = £0.0042 (0.42p)
What are possible pros of any electrical device?
Uses less energy
Cost-effective
Can be used in areas without mains electricity
How can we tell how useful a machine is?
The amount of energy wasted
What are the nine types of energy?
Kinetic Heat (thermal) Light Gravitational potential Chemical Sound Electrical Elastic potential Nuclear (Kids Hate Learning GCSE Energy Names)
What is the conservation of energy principle?
Energy can be transferred, stored, or dissipated, but never created or destroyed
What is dissipation?
When energy spreads out and is lost
What types of energy are involved in the function of a TV?
Electrical energy -> light, sound, and heat energy
What types of energy are involved in the function of a battery?
Chemical energy -> electrical and heat energy
