Hi Sarah,
There are two common processes currently used to generate electricity.
Nowadays, most electricity is generated by electromechanical generators. A generator is a device that converts mechanical energy into electrical energy through the action of turbines. Diverse sources of energy can be used: hydroelectric (the movement of water), geothermal, wind, combustion (oil, coal or gas) and even nuclear fission. No matter what the source is, the principle is the same. For example, in a nuclear power plant nuclear energy is used to generate heat, which converts water into steam that turns turbines.
Electric generator. Image adopted from Wikipedia.
The operating principle of electric generators was discovered by Michael Faraday in 1831. According to Faraday's law, changes in a magnetic field nearby an electric circuit induce an electric current. Such changes can arise from changes in the field, repositioning of the field source or repositioning of the circuit. The current is usually an electron flux.
In the context of this article, the significance of the induction is therefore that mechanical energy can be converted into electrical energy. The core of a generator is a cylinder that contains several magnets that envelope the center of the generator, which consists of an axle that surrounds electrical wires. The rotational movement of the axle changes the position of the electrical wires in relation to the magnetic field, and an electric current is induced. Another option is to turn the magnets around a stationary axle.
Image adopted from Wikipedia.
Another way is to generate electric power from solar energy, through the usage of photovoltaic cells (also known as solar cells). The principle here is based on the photovoltaic effect, an aspect of the photoelectric effect.
The photoelectric effect was first described by Heinrich Hertz in 1887, elucidated by Albert Einstein in 1905 (for which he was awarded the Nobel Prize) and demonstrated through experimentation by Robert Andrews Millikan in 1912-1915 (another achievement worthy of a Nobel Prize). The photoelectric effect describes the release of charged particles (electrons) from matter as a consequence of absorption of electromagnetic radiation. The photovoltaic effect, in fact, was described years earlier (1839) by Alexandre Bacquerel, who observed that when he directed a light beam at an acidic solution of silver chloride, an electric current would begin flowing between two platinum electrodes immersed in the solution.
A photovoltaic cell is comprised of semi-conductive materials. The light absorbed in the cell leads to separation of electric charges and hence to an electric potential difference (voltage) and to the flow of electric current once a circuit is closed.
Image adopted from Wikipedia.
Dr. Liran Shimshi
Department of Physics of Complex Systems
Weizmann Institute of Science
English translation:
Dan Blat
Department of Immunology
Weizmann Institute of Science
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