Electricity always seeks to go into the ground. Why? The basic principle is that electricity always seeks the path of least resistance.

The definition of electrical current is the movement of electrons from a higher energy level (for example, the 120 volts of an average hair dryer) to a lower energy level (for example, the 0 volts of the ground). The path of least resistance is the path from a higher to a lower voltage level. Since the earth is at zero volts, electricity will always seek to go to the ground. Understanding this principal is important in learning about electric conductors and insulators.

Insulators/Conductors
Some materials are resistant to the flow of electricity. These materials are called "insulators." Other materials allow electrons to move freely through them. These are called "conductors."

Examples:

Within the home it is typical to have conductors covered with an insulator to keep the electricity controlled, such as a rubber-covered electric cord. However, the mere presence of insulators is not a guarantee of safety. A variety of circumstances can compromise the integrity of insulators. For example, if the rubber covering a wire is split or broken, it would not protect a person from the electricity in the wire.

Transmission and distribution power lines are obviously conductors, but there is insulation material where the lines are attached to the towers and poles supporting them. This keeps electricity from leaving the lines and traveling down the support structures. There is no insulation on the lines themselves. It would be impractical to insulate such lines, and the integrity of such insulation could be compromised.

Electricity will take any path it can to the ground – and that’s when injury and harm can occur. To avoid an undesired path to the ground, lines and transformers must be physically separate from activity that might create a path. There are stringent national codes governing the distances above ground, and from structures, for the construction and maintenance of electrical lines. In addition, security measures must be followed to isolate energized equipment located on the ground.

Electrical injury
An electric shock results when an electric current flows through the human body as it seeks its path to ground. The body gives electricity a path to ground when it contacts a conductor carrying electricity and, at the same time, is contacting "ground," an object at zero voltage level.

The amount of current flowing through the body determines the extent of the injury. It is important to understand that the human body is a good conductor or electricity, primarily because of its water content.

Different current flows cause different sensations in the body:

Current is the flow of electrons and is measured in amperes (amps). A milliamp is .001 amp.

To give you an idea of how big (or small) these amounts are, a typical household circuit can supply 15-20 amps. Here are some typical currents for appliances:

Our brains are loaded with tiny nerve ends that provide transmitting service to the muscles. Muscles, in turn, provide motion for body functions such as the heart and lungs. An additional electrical impulse can cause the heart to speed up its pumping or stop functioning, or cause the lungs to stop taking in air. Depending on a number of variables, a small flow of electric current can do extensive damage.

The rule of thumb for an electrical shock victim is: Do not attempt to aid the victim until the source of the current is shut off, or the victim is no longer a path to ground.  Touching a person who is in contact with a current source will not remove the path to ground. In fact, touching a person in this situation provides the current with another path to ground through the rescuer. Rescuers can provide no help to victims if they become victims themselves! Normal instincts to provide assistance must be checked long enough to analyze the situation. Despite your very strong desire to help, wait until the contact with the current source no longer exists or the current source is turned off.

The length of exposure to electric current, the path of current flow, and the size of surface area of electrical contact can affect the severity of the shock. Very small currents can cause spastic action, but recovery can be rapid; slightly larger currents can cause muscle paralysis. In the event of paralysis, artificial respiration or massage must take place as quickly as possible to minimize damage to the brain from lack of oxygen. A condition known as ventricular fibrillation can occur with currents of 50 to 200 milliamps and will continue until something is done externally to restore regular heartbeat. Immediate first aid can save a victim whose heart has actually stopped beating and whose lungs have stopped pumping. Rapid action by knowledgeable persons can prevent body damage and save lives; however, heed the "rule of thumb."

Higher currents can result in electrical burns where tissue is destroyed. Even if burn injury is not visible, the current has traveled through the internals of the body so the burn effect may be beneath the skin.

Knowledgeable medical practitioners should always check victims of severe shock.