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In ac supply positive cycle is equal to negative cycle then given voltage is taken and fed back to mains then why we pay electricity bills?

pankaj prasad
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    It ain't about the voltage. It's about the energy. You are billed based on the energy provided to do the work you need it to do - that's why one is billed based on kilowatt-hours and not volts. – Adam Lawrence Apr 30 '18 at 13:12
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    And the infrastructure that continuously brings the energy to your house. – Wesley Lee Apr 30 '18 at 13:15
  • One pays the electricity bill because they (1) need electrical energy to do work and (2) don't have infrastructure to generate their own electrical energy, meaning they need to buy it from someone. – Adam Lawrence Apr 30 '18 at 13:17
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    It is like a bow saw, you push and you pull and the saw is back to the begin position. But the movement has done some work with the push and the pull. – Oldfart Apr 30 '18 at 13:21
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    Imagine a simple resistive heater. You apply a DC voltage across it - a current flows - power is dissipated as heat. Now swap the voltage source around to that it is now "negative". Does your resistive element now suck heat in "creating cold"? No. It doesn't work that way. – brhans Apr 30 '18 at 13:21
  • It reads to me like OP's posted a comedian's gag for a laugh. Voting to close. – TonyM Apr 30 '18 at 13:48
  • See https://electronics.stackexchange.com/q/233851/4512. – Olin Lathrop Apr 30 '18 at 14:41
  • Well there is no real reason other than capitalism. You see the inventor of the AC generator (Nikola Tesla) wanted it to be free, but David Rockefeller refuse to give him any R&D money unless he could stick a meter on it. So that is why the power meter exists. – drtechno Apr 30 '18 at 16:18
  • ... because if we don't we get cut off? – Jules Apr 30 '18 at 17:18
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    @drtechno But... it costs a ton of money to generate the electricity used by 1st world countries. How do you expect that to be free? – Matt May 01 '18 at 03:30
  • There are several methods to make electricity that doesn't require fuel that burns, and other nuclear methods that are not radioactive either. Its just sad the technology is suppressed by the greed of man. Maybe when money holds no value in the world, man can advance. I personally know at lease a dozen ways to generate electricity. – drtechno May 01 '18 at 11:33

3 Answers3

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You are billed for Power.

Power is Volts x Amps

  • When V is +ve, A is +ve, +V x +A = +Power
  • When V is -ve, A is -ve, -V x -A = +Power

So Power is always positive on both half cycles, and you will always get a power bill.

But you don't have to pay it...

Henry Crun
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  • Right: important thing to note is that the current always flows from the side of the circuit with high voltage to the side with the lower voltage, so the signs are always in agreement with each other, so power is always positive (unless you're actually supplying current from your own stored charge somewhere...). – Jules Apr 30 '18 at 17:16
  • when current lags or leads then at some points the power will be negative then energy meter calculate that power?? or fed back to the mains? – pankaj prasad May 01 '18 at 04:14
  • reactive current does not result in power, as it is in quadrature to the voltage (90 degrees). You don't pay for it, and it doesn't heat up your dinner. Another way to look at it is reactive V x A is positive half the time, and negative half the time, and sums to 0 – Henry Crun May 01 '18 at 04:18
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In any electrical circuit voltage is taken through a load and fed back. That does not mean the work was done for free and would break the first law of thermodynamics if that was true.

You are billed for energy, not voltage. Power = Voltage * Current. Your home does not consume voltage, but the more devices you power the more current you draw. That is why you are billed in kWH (Kilowatt hours). Watts are a measurement of Power. Watts consumed over time is a unit of energy.

Impossibear
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Power is voltage x current and, if the voltage is negative then so is the current.

  • Negative x negative = positive power
  • Positive x positive = positive power
  • i.e. YOU get billed.
Andy aka
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