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Current Electricity

  1. Jul 12, 2015 #1
    In Indian standard electric supply at homes is of 220V and 50Hz, What is the physical meaning of Voltage 220V? Does Voltage means Potential difference? I know that potential difference(pd) between two points is the work-done per unit charge to move it between the two points. Is 220V the pd between the power station nearby and my home wiring to the appliance?
    Confused :(
  2. jcsd
  3. Jul 12, 2015 #2


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    Gold Member

    Yes, it is potential difference. In electronics, we usually call this quantity as voltage. When we say voltage, for example, 5 V, it is the potential difference between two point. Normally when electronics is powered from power line, not battery, ground (connection to earth, I mean surface of the soil in this planet. The soil of this planet is considered as infinity reservoir of charge) is reference potential as zero. All most devices has ground connection for voltage (potential) reference.

    220 V is voltage difference between two wires of powerline (one is for forward current to device and other is for its returning.) The return path is eventually connected to earth thus we treat this line as 0 voltage when low frequency and low current are used.

    Output of power stand has very big voltage and this voltage is down-converted to 220 V in house via transformer.
  4. Jul 12, 2015 #3


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    Staff: Mentor

    You have two wires into your house. If you were to measure the potential difference between them as function of time, you would see that it is a sine wave with a frequency of 50 cycles per second and a peak-to-peak amplitude of about 340 volts. 220V is what you get when you calculate the root-mean-square (google for "rms voltage") average of the potential difference between the wires over time, and is the best measure of the amount of work that will be done by a given current flow.
  5. Jul 12, 2015 #4


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    Staff: Mentor

    Note that this is only strictly true for direct current (DC), whereas the line voltage that OP is asking about is alternating current.
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