To work around electricity safely, it is necessary to understand how it acts, how it can be directed, what hazards it presents and how these hazards can be controlled. It is necessary that you know the basic terms that describe electricity and their meaning in order to understand the hazards of electricity and how to be able to implement safe work practices. For the purpose of this training, we are going to use the terms current, amperes, volts, ohms, and conductors. To explain these terms, it might be easier to compare water in a garden hose to electricity in a wire. We will use simple analogies to define them.
Electrical current may be thought of as the amount of electricity flowing in a wiring system, like the amount of water flowing through a garden hose. The rate of flow of electricity or current is measured in amperes. Similarly, the water flowing through a garden hose is measured in gallons per minute. The water pressure in the hose is measured in pounds per square inch, whereas electrical pressure is measured in volts. We must also understand that the higher the pressure, the higher the voltage. Resistance can simply be thought of as the condition that restricts flow, like friction in the case of flowing water. The unit of measurement for electrical resistance is ohms. Resistance to the flow of electricity, or ohms, varies widely according to material. An insulator such as rubber or glass, provides tremendous resistance to the flow of electricity. Some substances, such as metals, provide little resistance to the flow of electrical current; these are called conductors. They conduct electricity without the loss of current. We have to be careful as to what we call an electrical insulator. For example, dry wood has high resistance but when saturated with water its resistance drops to the point where it will readily conduct electricity.