by Alwin Templar

Created on: August 05, 2009

Like most good inventions, the DC electric motor is both simple and ingenious. It is a device that takes electrical energy from a power source such as a battery and converts that energy into kinetic energy by means of electromagnetism. This conversion results in a rotating axle that can be used to do all sorts of mechanical work.

The easiest way to understand the workings of a DC motor is to describe the flow of electricity from the power source to the motor and back by means of two wires (an electrical circuit), and examine each stage in turn.

* The battery

Within atoms there are particles called protons, neutrons and electrons. Different kinds of atoms have different amounts of each, but essentially for every proton in the central nucleus there is a corresponding electron orbiting it. Each electron has a negative charge, which means that it is surrounded by a force field called an electrostatic field. The electron's corresponding proton in the atom's nucleus exhibits a force of equal strength but of opposite polarity - it has a positive charge - and because 'opposites attract', electrons and protons hold each other in balance.

However, in some atoms the electrons that orbit furthest away from their protons are only loosely held and can be affected by forces outside the atom. Such electrons can jump from atom to atom and so we call them free electrons. Free electrons normally move randomly, but when a force is used to make them all flow in one direction then we have an electric current. Such a force is called an electromotive force and is best pictured as a form of pressure forcing electrons to flow, much like water pressure forcing water to flow through a garden hose.

A battery is essentially a container in which, due to a chemical process, two separate materials have an imbalance of electrons (one with too many and the other with too few). The excess electrons in one material want to move to the other in order to balance the charge (or equalize the pressure) but to do this they need a means of travel.

The best means is a material that contains free electrons and so allows a current to flow. Such a material is called a conductor and copper wire is a perfect example. When the wire is connected from one terminal to the other, from the negative terminal to the positive, a circuit is created and the electrons flow. The flow of electrons from a power source, around a circuit and back to the source is called direct current (DC). If we add an electric motor

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