What is grounding?

   Electrical grounding, or earthing, is a common return, a completion of the circuit, for many electrical circuits. The earth can be used as this common return path, hence the term grounding. Often the metal frame-work on which electrical apparatus is mounted, or a heavy conductor, may be called a ground, although actual contact with the earth may not be made. In telegraph and telephone circuits the earth may be used as a common return for all or part of the circuits. Radio transmitters and receivers may also make use of the return effect of the earth's conductivity or capacity.
   As a safety feature, electrical power lines usually have one wire connected with the earth; this connection is usually carried through to the outermost electrical connection on all light fixtures. Accidental contact with a light fixture properly connected in this way will do little harm. (Since all plumbing is grounded, one should carefully avoid touching any plumbing or water flowing from the plumbing while contacting any electrical fixture.) Electrical machines usually have their frames grounded by a special ground wire that may be provided in the cable leading to them. Household washing machines, ironers, and electric stoves, may be so protected.
   Electric street cars, elevated trains, and electric trains often use the rails as a return ground connection. Vehicles such as automobiles, airplanes, and boats usually have one side of electrical circuits connected to the metal framework, and thus this framework may become the common return path for many circuits.