Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Home wiring

  1. Apr 19, 2004 #1
    Just curios. Why do the electrical outlets in my home have a positive, negative, and a ground? With circuits that I am familiar with, if you have a positive and a negative connected, there is no need for a ground. Does anyone have an explanation?

  2. jcsd
  3. Apr 19, 2004 #2


    User Avatar
    Science Advisor

    Actually, your house has a "Hot" a "Neutral" and a ground wire.

    The hot is fed 120V AC and since we need a complete circuit the neutral is used to complete the circuit.

    The big difference between neutral and ground is that ground should never have any current on it and is therefore safe to hook to the outside case of electrical devices to use as a means to protect people from shocks.

    In fact, if you look at a GFCI (Ground Fault Circuit Interrupter) that will be on any outlet near water (kitchen, bathroom, or outside outlets) there is circuitry that will open the circuit breaker if it senses ANY difference in the current on the hot and neutral wires. Since they are the two parts of the circuit, any current not flowing the complete loop must be going somewhere else (like in the bathtub) so therefore it interrupts the circuit well before enough current flows to trip the breaker by heating it, which may never happen even though a very unsafe condition may exist.

    So we need the ground to be really safe. The exception is double-insulated equipment which uses only the two plug lugs of hot and neutral and the safety is provided by the design of the device. For example, a double insulated drill may have a metal drill chuck but it is completely isolated from the eletrcial circuit with electrical insulation.

  4. Apr 19, 2004 #3
    does the nutrual wire go back to the circut breaker to complete the circut?
  5. Apr 19, 2004 #4


    User Avatar
    Science Advisor
    Gold Member

    It does not go to the breaker itself, but it goes to the neutral bar in the panel. If you own your own place, take the cover off and have a look.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook