What is the purpose-of grounding an outlet?

Answer 1

Answer for USA, Canada and countries running a 60 Hz supply service.

US NEC:

The grounded conductor, also known as neutral, is the return path for the circuit, operating in concert with the hot conductor.

It is not to be confused with the protective earth grounding conductor.

Neutral is white. Ground is bare copper or green. Hot is some other color than white, usually black or red.

A grounded conductor is used to limit the potential voltage of the hot conductor with respect to ground to no more than 120V. If the neutral circuit were not grounded, it is possible that hot voltage could rise to the level of the distribution circuit, typically 7.6kV, and that is an instantly lethal value.

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The above answer is correct but could be very confusing to a person who is not trained as a skilled electrician.

The neutral conductor in a circuit can more simply be referred to just as "the neutral" - even though it is grounded back at the main breaker panel - and the protective grounding conductor should be referred to as that or just as "the grounding" conductor.

For more information see the answer to "How does the ground or earth wire of an appliance protect a user if there is a fault with that particular appliance?" and also the other Related Questions shown below.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer 2

It prevents current from flowing through your body from the hot side of the power to ground instead of flowing from the hot side through an appliance and back to the neutral side of the power outlet. The neutral side is not the same as ground for this purpose.

Normally 100% of the power flows from the hot side through an appliance back to the neutral side of the outlet. If it detects current going from the hot to ground it assumes there is a problem and interrupts the circuit.

They can also falsely trigger due to moisture providing a path to ground for the power in a poorly ventilated shower room or a wet outside outlet.

Answer 3

An inaccurate description, technically

A grounded outlet has a wire that runs to a metal plate or frame that is buried in the ground. This is a safety device to help prevent someone from getting an electric shock because electricity always wants to take the shortest route to the ground.

If you attempt to mess with a non grounded circuit you may get shocked because the electricity will go through you to get to the ground. On a grounded outlet, the current will go straight through the grounded wire, because metal is a better conductor.

Normal American-style outlets have 3 holes, two straight conducting sockets and a bottom grounding socket.

However, some extension cords may not have 3 holes, so they are not grounded.

The male end of a cord - the end with prongs, not holes - also matters: if it does not have prongs that go into all three holes, it is not grounded.

Some better descriptions

The ground wire is connected to the outside metal casing of the appliance. It guarantees that if somehow the live or "hot" wire in the appliance shorted to the case, you won't get a shock - because the short circuit current will go to ground and not through you - and, in doing that, it will trip the breaker to cut off the supply of current.

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The purpose of the ground wire on an appliance or in a house branch circuit is to provide a low impedance low resistance return path for the fault current to return to the distribution panel. This high return fault current will cause the circuit's breaker to trip and disconnect the fault.

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The ground wire usually doesn't have anything to do with the normal electrical functioning of an electrical appliance but - because the ground wire is connected to the chassis or casing of the appliance - if an electrically 'hot' wire breaks or its insulation chafes so that it touches the chassis or casing, it will be shorted to ground via the ground wire, causing a very high current to flow in the 'hot' wire.

That high current will cause the circuit breaker to trip or a fuse to blow, thus cutting off the current and preventing the chassis or casing from electrocuting the user. Shutting off the current should also prevent the wires in the circuit from heating up so much that they catch on fire. Such a fault can easily be the cause of a serious house fire.

Answer 4

The main purpose of installing a ground wire to a receptacle is to provide a return path to the breaker panel to trip the circuit breaker. I have seen a hot water kettle that has had a fault and the whole body of the kettle became up to the potential of 120 volts. When the kettle was filled a spark jumped from the kettle to the tap. If the person had touched the body of the kettle and turned the tap on they would have taken a extremly bad shock from one hand to the other hand across the chest. This receptical did not have a ground wire attached to it. If the receptical had a ground wire on it, as soon as the kettle was plugged in it would fault and the breaker would have tripped and shut the voltage off. NEVER CUT GROUND PINS OFF OF EQUIPMENT.

Answer 5

The purpose of grounding an outlet is for personnel safety. In electrical single phase installations the ground wire is used to carry a fault current back to the distribution and trip trip the breaker of the circuit that the fault was on. Without this ground wire a person could become the ground and receive a sever shock.

Answer 6

Grounding in an electrical circuit is an essential safety feature which is compulsory in the electrical regulations.

Answer 7

Safety.