# Power and voltage are the same thing?

1. Aug 30, 2016

### lastfsdfsd23

2. Aug 30, 2016

### Staff: Mentor

Power is voltage times current. P=V*I.

3. Aug 30, 2016

### lastfsdfsd23

it's a law

4. Aug 30, 2016

### cnh1995

Yes. Before going for electrical power, you should understand the terms voltage and current.
Voltage is the difference in electric potentials of two points in a circuit which drives a current through the circuit. Power is the product of voltage and current.

5. Aug 30, 2016

### lastfsdfsd23

yeah. that's it. i understand.

6. Aug 30, 2016

### lastfsdfsd23

7. Aug 30, 2016

### jim hardy

@lastfsdfsd23

It's just like mechanics. Go back to freshman physics..
Force tries to move something, but no work is done until that something moves.
Work done is Force X Distance moved.
Power is work done per unit time, ie Force X distance/time = Force X Velocity .

Volts try to move electric charge. No charge moved = no work done.
Work done is Volts X amount of charge moved .
Power is work done per unit time, ie Volts X amount of charge moved per unit time = Volts X Amps.

That should get you started.

Last edited: Sep 4, 2016
8. Sep 9, 2016

### Tero

I remember this one quite easy to remember explanation of the voltage, current and power:

Imagine a waterfall a tall waterfall. The height of the waterfall is the voltage in electrical system called potential difference. Higher the waterfall faster the water will fall down so to speak. Then the amount of water which passes the waterfall is the current. And the "work" let's call it power is in the actual falling of the water on that waterfall.

9. Sep 9, 2016

### jim hardy

The work shows up as warming of the water, erosion of the rocks, noise, and any other energy pathway you can think of.
A BTU being 550 er i mean 778 foot-pounds , and Niagara Falls being 167 feet high
you should find the water flowing away at bottom of Niagara warmer than upstream by about 167/778 = 0.21 degreesF .

Do not confuse gravity with coulomb force on charges in a field.
Else you'll think 'electricity' is attracted to 'ground'
which is a widely believed mistake.

Last edited: Sep 9, 2016
10. Sep 10, 2016

### jaus tail

[QUOTE="j
Do not confuse gravity with coulomb force on charges in a field.
Else you'll think 'electricity' is attracted to 'ground'
which is a widely believed mistake.[/QUOTE]

i thought ground was at zero potential n acts like sink for currents in case of earth faults...like current would flow into the ground...

11. Sep 10, 2016

### jim hardy

That's a common misconception.

Ground only completes the circuit back to the source.
It's not at all a "sink" like earth is for rain .
"Ground" is best thought of as just another wire that goes most everywhere.. If your source is not connected to "ground" no current will flow into a "ground fault" .

Most systems that we encounter are connected solidly to "ground" so that a ground fault will trip the overcurrent device thereby announcing its presence.

There exist in industrial settings systems that are "grounded" by a high resistance so that a "ground fault" will cause only small current to flow. Limiting fault current does two things for you:
1. Limits energy input to the fault. You don't want a high current arc inside an expensive machine. It's easier to repair the damage from a small arc of just a few amps than than that from a multi-kiloamp explosion.
2. Allows a machine to keep running until you can start a backup or arrange to shut it down without upsetting the rest of your plant.

I recommend you read "IEEE Green Book" . It will firmly implant the basics of "grounding" .