4) What are the different sources of electric potential (electricity)?
Answers
Answer:
Electromagnetic Induction - Generators
When a conductor is moved through a magnetic field, the electrons in the conductor experiences
a force that causes an electric current. Kinetic energy of water or steam forces conductors to
rotate in a magnetic field ( e.g. Hydro-, nuclear-, fossil-fuel-powered electric generators).
3. Mechanical Sources - Piezoelectricity
Quartz and Rochelle salt crystals create a small electric potential when mechanical force or
stress is applied to them. The potential difference depends on the amount of force applied.
Piezoelectricity is used in some cigarette lighters, crystal microphones and electroscopes.
4. Thermal sources - Thermoelectricity - Thermocouple
Thermal (heat) energy is converted into electrical energy by means of a device called a
thermocouple. It consists of two dissimilar metal conductors joined at the ends, which are kept
at different temperatures. This causes a potential difference to be developed in the loop.
Thermocouples are used to detect flames and to find the temperature of molten metal. (e.g., gas
pilot light safety system: Current keeps gas valve open as long as flame is lit)
5. Light Sources – Photo-electricity - Photo cells
Light energy may be used to do work on electric charge and to produce an electric potential
difference. When a short wavelength of light strikes certain metals, the surface electrons are
removed from their atoms. This is referred to as the photoelectric effect.
Solar cells, which are thin wafers of semiconductors, can produce a small potential difference
when light strikes them. (less than 1 V ) It takes a large number of solar cells joined together to
produce a large enough potential difference to be of any practical value. These solar cells are
used in calculators, satellites, and space probes.