Generating electricity

Where does electricity comes from?

Electricity is a very useful form of energy. It comes from special factories called power stations.

• In most power stations the following steps are necessary:

1.  The fuel is burned to release heat energy.
2.  This energy is then used to heat water (in the boiler), changing it into steam.
3.  The steam is then used to turn the turbine.
4.  The turbine turns the generator which produces electricity.
5.  The electrical energy produced travels through wires to houses, shops and factories.
6.  Machines called transformers change the voltage of the electricity travelling along the wires.

The energy changes in this process are:

Chemical energy → heat energy → kinetic energy → electrical energy

• In a hydroelectric power station there are no boilers. The kinetic energy of the falling water is transformed directly into the kinetic energy of the turbine blades.

The energy changes in this process are:

Gravitational potential energy → kinetic energy of water→ kinetic energy of turbine→ electrical energy

Paying for your electricity

The electrical energy from a power station travels along a network of wires called the National Grid to our homes. There it passes through an “electricity meter” for measuring the electrical energy we use. The meter measures this energy in kilowatt-hours (kWh). Every two months we receive a bill for the electrical energy consumed.

Most appliances in our homes need electrical energy to work, but they use the energy in a different way. Some, like electric heaters, use the energy quickly. Others, like light bulbs, use the electrical energy much more slowly. The rate at which energy is being used is called the power of the appliance. We measure the power in watts (W) or kilowatts (kW). One kW is 1000 W.

The power of some common domestic appliances is:

Personal computer hardware [Part 3]

Video card

It is also called graphics card and it function is processing the graphics output from the motherboard and send it to the display.

Keyboard

A keyboard is an arrangement of buttons that corresponds to a number, function or letter. It is the main input for typing text but it is also used for playing videogames on the computer.

Mouse

It is a small slideable devide which is used to click and drag items on the computer's display.