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Are "unequal grounds" a real thing?

By Envergure
Feb 2, 2010
  1. Hi,

    I've heard that "grounded" connections in power outlets can have different voltages in different areas, for example a plug in your kitchen may be a few millivolts different from one in your bathroom, and that a "ground" plug in England may be thousands of volts different from one in, say, Japan. This, supposedly, sometimes causes problems in stadiums and other large buildings where audio systems are spread out over large areas. I imagine it would make internet transmission under oceans between continents difficult.

    Is there any truth to this?
  2. captaincranky

    captaincranky TechSpot Addict Posts: 14,381   +3,602

    The reason they call it a "ground" is because it doesn't have any electromotive potential of its own. Therefore, any "voltage" a ground is conducting has to be supplied by a positive voltage source.

    A voltage differential between different rooms in a house might be better explained by increased resistance due to longer wire runs, thereby resulting in a minute decrease in measurable voltage.

    There are various mechanisms whereby stray AC current can induce "hum" into electronic equipment.

    As to voltage differences, Europe uses "220" volts AC, but the US uses "110".

    The US 110 volts "standard" fluctuates a fair amount dependent on time of day, load, and source. The "60" Hz, (or cycles per second), is controlled very closely. "Synchronous" AC electric motors depend on it.
  3. jobeard

    jobeard TS Ambassador Posts: 12,498   +1,433


    Europe is 220v 50hz while U.S. is 120v 60hz, both single phase.

    Also, a GFI: Ground Fault Interrupter, is designed to 'open' the cirucit whenever current is
    sensed in the 'ground' leg. As this should never happen, it indicates a bad condition in the
    equipment attached or the supply side wiring.

    A/C hum (at the supply frequency) is ALWAYS an issue of inadequate shielding and proper grounding of the equipment, in particular, in the input signal sources, eg microphone leads.
  4. kokoko

    kokoko TS Enthusiast

    thanks for the info.
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