Electrical devices are extremely useful. They transform electrical energy into whatever form of energy we need at the flick of a switch.
Common electrical devices include:
- Electric mixers
Electrical energy is energy transfer due to an eletric current.
The power of a device is the rate at which it transfroms energy.
The unit of power is that watt. A device with the power of 1 watt transforms 1 joule of electrical energy to other forms of energy every second.
Often a watt is too small a unit to be useful, so power may be given in kilowatts, 1 kilowatt = 1000 watts.
Using Electrical Energy
Companies that supply mains electricity charge customers for amount of electrical energy used, and this is measured in kilowatt hours. A kilowatt hour is the amount of energy that is tranfered by a one kilowatt device when used for one hour.
The amount of energy in kWh transfered to a mains device can be found by multiplying the power of the device in kilowatts by the time it is used for in hours.
The eletricity meter in a house records the number of kilowatt hours of energy is used. If the previous meter reading is subtracted from the current reading, the electrical energy used between the readings can be calculated. The cost of the electrical energy supplied is found by multiplying the number of kWh by the cost per kWh, which is given on a electricity bill.
REMEMBER: kilowatt hours is a unit not a measure of power or energy.
The National Grid
In Britain, electricity is distributed through the National Grid. This is a network of pylons and cables that connects power stations to homes and other buildings. Since the whole country is connect in one system, power stations can be switchd in or out according to command.
In power stations, electricity is generated at a particular voltage. The voltage is increased by step up tranformers before the electricity is transmitted across the National Grid at about 132 kilovoltage or more. This is because transmission at high voltage reduces energy loss in cables, making the system more efficient.
It would be dangerous to supply electricity to the consumer at these high voltages, so a step down tranformers are used to reduce the voltage to 230 volts.