Wind turbines on a wind farm Electricity is a type of energy that gives us heat and light and drives machines. To be useful, electricity must be made to flow in a current. In 1831 the British scientist Michael Faraday used a magnet to produce electricity. He moved a loop of wire over the magnet, causing an electric current to flow along the wire. This principle is used to generate electricity in power stations today.
Electricity and magnetism are two aspects of the same force, called the electromagnetic force. They are so closely linked that one can produce the other. An electric current flowing in a cable produces a magnetic field around the cable. A magnetic field moving near a cable causes electricity to flow along the cable. Electromagnetism is the basis of how both generators and electric motors work.
Turbines and generators
An electric generator is a device that converts mechanical energy to electrical energy. It forces an electric current to flow through a circuit. In thermal power stations, coal, oil or gas are burned to boil water, producing steam to provide the mechanical energy to drive a generator. The steam rushes through pipes and turns a bladed wheel called a turbine. The turbine is connected to the generator, which consists of a huge magnet surrounded by copper wire. The turbine makes the magnet spin, thus producing an electric current in the wire.Turbines inside a power stationGenerators provide nearly all of the power for electric power grids. The source of mechanical energy may be flowing water, the wind, tides or waves, and it may be produced from heat energy from inside the Earth, heat energy from the Sun, or nuclear energy.
Hydro-electric power stations use fast-flowing water, flowing downhill under the force of gravity, to turn turbines. The water from rivers is stored in a reservoir behind a dam. The power station is located in front of, or contained inside, the dam. Some of the water from the reservoir is allowed to flow out through inlets below the water level and along pipes, called headraces or penstocks, into the turbines inside the power station. Each turbine has angled blades that are spun by the force of the water rushing past them. A shaft connects the turbines to generators.
Hydro-electricity does not produce greenhouse gases, and the dams are useful both for supplying water to cities and farms and controlling flooding downstream. But the dams can disrupt local wildlife and, because of the enormous weight of water contained in the reservoirs, cause earthquakes.
A “solar furnace”
Coal and oil-fired power stations cause pollution. They also emit significant quantites of carbon dioxide, a greenhouse gas, into the atmosphere and are considered to be a major cause of global warming and climate change. Fossil fuels, once used up, cannot be replaced. Leaks of radioactivity from nuclear power stations are a potential hazard. So today alternative methods for generating electricity are being turned to.
Wind turbines on wind farms, solar power (in which solar panels store sunlight for conversion to electricity), tidal and wave power are all being used. These, like hydro-electric power, are renewable energy sources, because the energy they produce is replaced naturally.
The electricity is sent from a power station along thick wires called cables. They are supported above ground by tall pylons. Along the way, transformers raise the voltage of the electric current, because transmitting high-voltage electricity is more efficient. Voltage is a measure of the force needed to make electricity flow.
The electricity goes to substations from where cables carry it to houses, factories, shops and offices. Substations contain transformers, which reduce the voltage of the current so that the electricity can be used in people’s homes. When we plug an electrical appliance into a socket, it connects up to mains electricity.
The cables from a power station are linked to form a country’s supply network or grid. This allows electricity to be sent to wherever it is needed. Electricity cannot be stored, so a constant supply flows through the cables and wires.
Consultant: Chris Oxlade
The first public power station is opened by Thomas Edison. In order to send power to customers’ homes, Edison also creates the first electric grid.
The first solar cell is made by American inventor Charles Fritts.
The first modern steam turbine, a turbine driven by pressurized steam, is invented by British engineer Charles Parsons.
The first nuclear power station is built at the University of Chicago, USA.
The first wind farm is put into use in Washington, USA.
See also in Earth