Electronics Principles V11

Clive W. Humphris


All matter is made up of a three dimensional lattice of atoms. An atom consists of a central core called the nucleus containing protons and neutrons around which orbit one or more electrons. Atoms are extremely small and millions of them are required to make up the smallest humanly visible object.

The simplest atom is that of the Hydrogen element which has just one proton and one orbiting electron. The number of electrons in orbit determines the type of material. The electron orbit is referred to as a shell. Each is given a letter K - N.

Electrons carry a negative (-) charge, whereas protons are positively (+) charged. An atom in its neutral state has an equal number of electrons to protons where the positive and negative charges cancel to achieve an electrical balance.

However, should an electron be forced to leave its orbit the atom takes on a positive charge and will therefore try to attract a negative electron from a neighbouring atom to regain its neutral state. The atom, which has just had its outer electron, pulled away in turn takes on a positive charge causing an electrical movement from one atom to another. This is the principle of current or electron flow. The direction of movement is determined by applied potential polarity.

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