Electrical energy Flashcards
Why are electrical appliances so useful?
They are so useful because they transfer electrical energy into any form we need at the flick of a switch.
Detail three common electrical appliances.
Detail how these appliances transfer electricity.
Tv - electrical energy to light and sound energy
Lamps - electrical energy to light energy
Electric mixers - electrical energy to kinetic energy
What is the power of an electrical appliance?
The power of an electrical appliance is the rate at which it transfers energy.
What is the unit of power and what is its symbol?
What does it mean if an electrical appliance has a power of 1 ….?
The unit of power is the watt, W.
An appliance with a power of 1 watt transfers 1 joule of energy to other forms of energy every second.
Often a watt is too small a unit to be useful, so power may be give in which other unit? What is its symbol?
How many watts is one of these equivalent to?
Kilowatts, kW
1kW = 1000 W
Power can be calculated using what equation?
P = E ÷ t Where: P is the power, W E is the energy transferred, J t is the time, s for the energy to be transferred
What is the efficiency equation in terms of power?
Efficiency = Useful power out ÷ Total power in (x100%)
Companies that supply mains electricity charge customers for the amount of electrical energy used in which unit?
kilowatt-hour (kWh)
What is a kilowatt-hour?
A kilowatt-hour is the amount of energy transferred by a one kilowatt appliance when used for one hour.
The amount of energy transferred to a mains appliance can be calculated using which equation?
E = P x t Where: E is the energy transferred, J P is the power, W t is the time, s for the energy to be transferred
How can the electrical energy used between two readings be calculated?
The electrical energy used between two readings can be calculated by subtracting the previous meter reading from the current reading.
How is the cost of the electrical energy supplied calculated?
Total cost = number of kWh x cost per kWh
When comparing the cost effectiveness of different appliance what six main factors should be considered?
Cost of buying the appliance Cost of installing the appliance The running costs The maintenance costs Environmental costs The interest charged on a loan to buy the appliance
What is the payback time of an appliance?
The payback time of an appliance is the time taken for an appliance or the installation to pay for itself in terms of energy savings.
