What is the difference between neutral and ground?

Discussion in 'General Electronics Chat' started by studiot, Sep 3, 2013.

  1. studiot

    Thread Starter AAC Fanatic!

    Nov 9, 2007
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    I have been asked a question that properly belongs in a thread for all to discuss, as in the title.

    Here is my response to kick off.

    Briefly the neutral is the return path to complete the circuit, in order for current to flow. In AC circuitry this is normally called the neutral and in DC circuitry it is often called the return or zero (sometimes it is erroneously called the earth)

    An ground (US) or earth (UK) is a point or body that maintains its potential, regardless of the flow of current into or out of it.

    Very often we connect the neutral or return to earth to tie its potential to something close to the surroundings for safety.
    The other conductor or conductors are then described as hot or live.
     
  2. MaxHeadRoom

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    Jul 18, 2013
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    This looks like a carry over from my rant in "The Art of Electronics" Thread?:p

    IMO Earth and ground has generally lost its meaning in the way it used so randomly now in normal electronic documentation usage' especially in the way it was used in the above publication without any reference to any other means of representing power common or their associated symbols.

    This is a general original definition.

    "Early developers of electrical systems theorized that the earth was an electrically neutral body, i.e. an equal number of negative and positive charges are distributed throughout the earth at any given time. Being electrically neutral, earth is considered to be at zero potential and establishes a convenient reference frame for voltage measurements. Noting that voltmeters read only the difference in potential between two points, absolute measurements can be made by using earth as a reference."
    (An 8,000 mile diameter spherical conductor)!

    If anyone wants a definitive reference, there is a book published by the IAEI, International Assn. of Electrical Inspectors entitled Soares Book on Grounding, also used to update the NEC.
    I picked up a recent copy for $1.00 on AbeBooks Clearing house!.

    The polarity, phase or live conductor in any supply may be connected to earth ground where it is now considered neutral.
    Max.
     
  3. studiot

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    Hello, Max.

    No it is not the electrically neutral or otherwise property that makes the planet an earth. There are also other bodies that can act as an earth, it depends upon the situation.

    The point is that in order to act as an electrical potential reference value, its potential cannot change.

    This is also the property needed for the other two uses of earth, viz safety and shielding.

    A safety earth potential remains steadfastly unchanged by a large fault current to earth.

    A shielding earth maintains the electric potential around the protected object at a fixed potential regardless of electromagnetic fields.

    I know that none of these are perfect an there are circumstance swhen we need to take real values into account but that is the principle of the ideal earth.
     
  4. MaxHeadRoom

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  5. MaxHeadRoom

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    In the case of AC where you have two conductors for 1ph, there is no considered neutral or return as they are both identical in effect and no reference is made for a neutral unless one is taken to earth ground.
    It is when one is earth grounded that one is considered a neutral.
    In a 3 ph Star wound secondary supply, the star point is usually considered the neutral and may or may not be earth grounded.
    Max.
     
  6. GetDeviceInfo

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    Jun 7, 2009
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    in AC power circuits, the neutral wire carries the unbalanced current, in a polyphase system. The neutral point in a polyphase circuit may or may not be grounded. Ground is a reference to an earthed electrode.
     
  7. studiot

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    Not necessarily.

    For instance most vehicles are electrically insulated from the planet yet their electrical systems have a designated earth or ground at one terminal of the battery connected to chassis.
     
  8. Raymond kunda

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    Aug 26, 2013
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    check the three phase connections in your book..............the reason we use the neutral is when the load is not balanced in a star connection....for instance if the Red phase,Yellow phase and Blue re not balanced we tap a neutral on the middle of the connection

    I don't feel old.
     
  9. GetDeviceInfo

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    that point is chassis common, and can be so regardless of polarity. The discomfort of static buildup is the simplest dis qualifier of a true ground concept.
     
  10. MaxHeadRoom

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    In the GM Factory manuals I have, they use the term ground AND the earth ground symbol in their schematics.
    Just another misuse of the term in my opinion, tending to make it meaningless?
    Max.
     
    Last edited: Sep 4, 2013
  11. GetDeviceInfo

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    I'm thinking that the terms have been misused commonly. The repetition of questions on this forum in regards to the topic is indicative.
     
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