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I'm really an electrical noob who tries to understand voltage, current and resistance. I know the formulas and can somehow come up with basic explanations about the physics of electricity. However, what I really don't get is the different effect of current and voltage in a circuit.

From what I understand is that power is voltage times current. I'd like to know some physical properties of a high voltage based power in comparison to a high current based power. So far I only know that high voltage power can be transmitted with much less losses. But what are other physical effects of the two types of power? How does a resistor react on high current vs. high power? I don't understand why 1000v with 1amp has a different effect on resistors than 1v with 1000amp. Maybe someone can provide me with some examples to understand the difference a bit better?

Thanks!

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marked as duplicate by Ignacio Vazquez-Abrams, Daniel Grillo, placeholder, Bence Kaulics, uint128_t May 28 '16 at 2:52

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  • \$\begingroup\$ Try reading about ohms law \$\endgroup\$ – PlasmaHH May 25 '16 at 18:59
  • \$\begingroup\$ @PlasmaHH has it right. How does current relate to voltage in their behavior in our physical world? V=IR. \$\endgroup\$ – John D May 25 '16 at 19:20
  • \$\begingroup\$ Hi, thanks for your answers. I was actually looking for some physical examples, not a formula. However, meanwhile I found this site which was perfect for a dummy like me ;-) learn.sparkfun.com/tutorials/… \$\endgroup\$ – gkunz May 25 '16 at 19:29
  • \$\begingroup\$ High current "1000amp" will need very thick wires and thick wires are expensive and bulky. It is much easy and cheaper to use a high voltage and low current. \$\endgroup\$ – G36 May 25 '16 at 19:51
  • \$\begingroup\$ One Volt is the amount of electrical force required to push one Amp of electrons through one Ohm of resistance. \$\endgroup\$ – b degnan May 25 '16 at 23:21
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1) The best explanation to remove the 'abstraction' is to think of water flowing through a pipe. The source of the water is the water pressure, equal to voltage. If the water is allowed to flow through the pipe, the flow is equal to current. If there is a 'kink' in the pipe or the faucet is not open all the way, this creates 'resistance' to the flow, but if the faucet is closed and no water flows, the water is at full pressure, regardless of a kink in the pipe.

2) So static water (not moving, as in a lake) can have lots of pressure, but no work is done unless the water is allowed to flow. Hence the simple DC equation: watts = amps x volts. To move the electric generators in a dam, a lot of water has to flow under high pressure, so as to push the turbine blades fast enough. One could say that a lot of current (amps) is flowing under a lot of pressure (volts) to do a lot of work (watts).

3) A lake is vaguely symbolic of a capacitor in that it traps water until it is needed. If the dam breaks all the water is set free over a short period and lots of damage can occur. If you use a pressure washer to clean your driveway, the pump increases the water pressure (voltage), but has a limit to the total amount of water it can pump out, based on the amount of water your faucet can supply (current).

4) A fat sewer drain pipe can move lots of water (current), but the water is under little pressure. Too much water flow and the water begins to come out of low lying sewer drains instead of draining away.

5) So to move water under high pressure you do not need a fat pipe, just a strong one. To move lots of water under little pressure, a fat pipe makes the flow easier. To move lots of water under high pressure you need both fat and strong pipes.

6) A kink (resistance) in a pipe with no water moving has no effect on water pressure (voltage). If you draw water from this pipe (current), then the kink (resistance) or a valve (variable resistor) will drop the water pressure (voltage) at the faucet, but not at the waters original source.

7) Please read the comments by others. They supply some simple but important math.

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As Feynman simply noted on his lectures power is a phenomena which does not change no matter what happens. In another word it is always conserved. When current moves through a resistor the dissipated power can be calculated to be R*I^2 for a DC current. For ac power other factors such as capacitance between power lines and their inductance causes the current to fluctuate in the grid which further increases the power loss. All this effects can be reduced by employing low current trick to some degree. By using high voltage you are dissipating lower power on power lines and more on the desired load. The total transferred power doesn't change. Think of it as using pressure cooker vs pot, as both accomplish the same task but the first the heat transfer mechanism dissipates less heat. Even though both are powered by the same fire source, the latter gets a lot less energy due to dissipation.

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