The switch's electrical source is a power generating station. A generator provides the pressure for the electrical current to travel through electrical conductors, or wires. Three factors determine the resistance of a substance to the flow of electricity. What it is made of. Substances with very little resistance to the flow of electrical current are called conductors .
Examples are metals.
Substances with such a high resistance that they can be used to prevent the flow of electrical current are called insulators . Examples are glass, porcelain, plastic, and dry wood. Therefore, although dry wood is a poor conductor, when saturated with water it becomes a ready conductor. The same is true of human skin. When skin is dry, it is a poor conductor of electrical current.