NOTE: This paper explains the theory and uses of the electric generator, and explains the differences between AC and DC generators. It also includes a glossary and a bibliography.
In its most basic definition, an electric generator is a machine that produces electricity. Generators produce almost all of the electricity used by people. They supply the electric power that runs machines in factories, provide lighting, and operate appliances in the home. There are two main types of generators - alternating-current (AC) generators (sometimes called alternators) and direct-current (DC) generators (also known as dynamos). Both types of generator work on the same principles.
How A Generator Works (Basic Principles)
A generator does not create energy - "energy cannot be created or destroyed, only changed from one form to another" (Sir Isaac Newton). A generator changes mechanical energy into electric energy. Every generator must be driven by a machine that produces mechanic energy.
For example, the large generators that provide electricity to Lae and the rest of PNG are driven by hydro power. The mechanical device that powers a generator is known as a prime mover. To obtain more electrical energy from a generator, the prime mover must supply more mechanical energy.
Generators produce electricity by means of a principle discovered independently by two physicists in 1831 - Michael Faraday of England and Joseph Henry of the United States. Faraday and Henry found that they could produce electricity in a coil of copper wire by moving the coil near a magnet. This process is called electromagnetic induction.
A simple generator (see Figure 1 below) consists of a single loop of wire turning in a magnetic field. Electricity is produced only while the loop is rotating. As the loop rotates, the two sides "cut" the magnetic lines of force. This...