Voltage sources

The following phenomena are the main sources that we use to generate voltage:

  • friction
  • magnetism
  • chemicals
  • light
  • heat
  • pressure

In each case, energy in one state is transferred into energy as current. No energy is lost or gained, it simply changes its form.

Magentism (electrical generators)

Magnetism is used as the voltage source in electrical generators and is by far the most common method of producing powerful and large currents at scale.

If a conductive wire is passed through a magnetic field voltage will be produced so long as there is motion between the magnetic field and the conductor. A generator is a device that generates current in this manner. Generators themselves need to be powered. They can be powered by steam from a nuclear power plant, water, wind, coal or other fossil fuels.

AC/DC

Depending on how it is wired, a generator can produce directed current (DC) or alternating current (AC):

  • Directed current

    • The electrons flow in only one direction

  • Alternating current

    • The electrons flow in one direction and then the other

Chemicals (cells and batteries)

The chemical creation of current is the physics behind batteries. Chemical current production produces currents on a smaller and less industrial scale than generators.

A chemical cell consists in two dissimilar metals such as copper and zinc. We call these the electrodes. They are immersed in a salt, acid or alkaline solution. We call these the electrolytes. The electrolyte pulls the free electrons from the copper electrode which leaves it imbalanced with a positive charge. The zinc electrode attracts the free electrons from the electrolyte giving it a negative charge, thus a difference of potential is achieved.

Light (photovoltaic cells)

Solar energy can be converted to electrical energy through solar panels which are large collections of photovoltaic cells.

When the surfaces of these cells are exposed to light, it dislodges electrons from their orbits around the surface atoms of the cell material. For each cell this only produces a very small amount of energy, therefore large quantities must be used.

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