This article provides information on the following six methods of producing electric power. Friction: Energy produced by rubbing two material together. Heat: Energy produced by heating the junction where two unlike metals are joined. Light: Energy produced by light being absorbed by photoelectric cells, or solar power. Chemical: Energy produced by chemical reaction in a voltaic cell, such as an electric battery. Pressure: Energy produced by compressing or decompressing specific crystals. Magnetism: Energy produced in a conductor that cuts or is cut by magnetic lines of force.
Friction
Friction is the least-used of the six methods of producing energy. If a cloth rubs against an object, the object will display an effect called friction electricity. The object becomes charged due to the rubbing process, and now possesses an static electrical charge, hence it is also called static electricity. There are two main types of electrical charge: positive and negative. Each type of charge attracts the opposite type and repels the same type. This can be stated in the following way: Like charges repel and unlike charges attract. Static electricity has several applications. Its main application is in Van de Graaff generators, used to produce high voltages in order to test the dielectric strength of insulating materials. Other uses are in electrostatic painting and sandpaper manufacturing. The course grains acquire a negative charge as they move across the negative plate. As unlike charges attract, the positive plate attracts the course grains and their impact velocity enables them to be embedded into the adhesive.
Heat
In 1821 Thomas Seebeck discovered that the junction between two metals generates a voltage that is a function of temperature. If a closed circuit consists of conductors of two different metals, and if one junction of the two metals is at a higher temperature than the other, an electromotive force is created in a specific polarity. An example of this is in the case of copper and iron, the electrons first flow along the iron from the hot junction to the cold one. The electrons cross from the iron to the copper at the hot junction, and from the copper to the iron at the cold junction. This property of electromotive force production is known as the Seebeck effect. This effect is utilized in the most widely employed method of thermometry.
Light
The sun's rays can be used to produce electrical energy. The direct user of sunlight is the solar cell or photovoltaic cell, which converts sunlight directly into electrical energy without the incorporation of a mechanical device. This technology is simpler than the fossil-fuel-driven systems of producing electrical energy. A solar cell is formed by a light-sensitive p-n junction semiconductor, which when exposed to sunlight is excited to conduction by the photons in light. When light, in the form of photons, hits the cell and strikes an atom, photo-ionisation creates electron-hole pairs. The electrostatic field causes separation of these pairs, establishing an electromotive force in the process. The electric field sends the electron to the p-type material, and the hole to the n-type material. If an external current path is provided, electrical energy will be available to do work. The electron flow provides the current, and the cell's electric field creates the voltage. With both current and voltage the silicon cell has power. The greater the amount of light falling on the cell's surface, the greater is the probability of photons releasing electrons, and hence more electric energy is produced.
Chemical
When a zinc electrode and copper electrode are placed in a dilute solution of sulfuric acid, the two metals react to each other's presence within the electrolyte and develop a potential difference of about 1 volt between them. When a conducting path joins the electrodes externally, the zinc electrode dissolves slowly into the acid electrolyte, The zinc molecule goes into the electrolyte in the form of positive ions while its electrons are left on the electrode. The copper electrode on the other hand does not dissolve in the electrolyte. Instead, it gives up its electrons to the positively charged ions of hydrogen in the electrolyte, turning them into molecules of hydrogen gas that bubble up around the electrode. The zinc ion combines with the sulfate ion to form zinc sulfate, and this salt falls to the bottom of the cell. The effect of all this is that the dissolving zinc electrode becomes negatively charged, the copper electrode is left with a positive charge, and electrons from the zinc pass through the external circuit to the copper electrode.