What's the difference between Watts, Volts and Amps?

[justinquinn]

What's the difference between Watts, Volts and Amps?

Trying to learn about power sources, etc...

Thanks!

[jpb]

In simplistic terms,

Amps measures the amount of charge flowing.

Volts measures the amount of energy expended per unit charge.

Watts measures the work done or rate at which energy is expended so its equal to Volts x Amps.

Now you're going to ask what charge is!

[c4757p]

Perfect. Another way to think about voltage, at least to help visualize it, is that is would be pressure, if electricity were water. Current (amps) would literally be the water current.

[mikes]

OH NOES! Google is broken again!

Seriously, do a search. You'll find much better, much more detailed, much easier to understand info that way than by asking someone to put something together just for you here.

[KD0CAC John]

Another tid-bit is depending on the application of what the device is doing , it will have different voltages , 12 volts for a car , 120 volt for you house .
There is a relationship that generally changes between amps & volts , as the number of volts is lower the number of amps are higher , example again , a car battery may have around 500 - 1,000 amps available at 12 volts to start the car and as little as 1 amp 12 volts to run an accessory in the car .
In your house your wall socket will have a limit of 15 - 20 amps at 120 volts .
The common measuring unit that combines volts & amps is watts .
So the car battery running the stater is 12v x 1,000a = 12,000 watts     
The accessory is 12v x 1a = 12 watts
The house socket 120v x 15a = 1,800 watts
The difference between either of the above is between DC - direct current for the car , and AC for the house , the watts are still the same .

[mariush]

[Strada916]

P = I x V
Where Power in Watts
I is current in Amps
and V as in Volts

There is the relationship.

[marmad]

The old standby analogy is water (although c4757p didn't carry it far enough) because most humans have been hit by a stream of water under pressure -  so they can picture it. But one important unit you left out which you should understand is resistance - it's the third leg of the tripod of Ohm's law (the other two being volts and amps), which means that if you know any two of them at a particular point in a circuit, you can always calculate the third.

So, the analogy: imagine a water faucet at the end of a pipe - that faucet (and all of the pipe leading up to it) is 'resistance' [ohms]. When the faucet is closed, you have infinite resistance (obviously) and no water flows. Now imagine the water - it's under pressure in the pipe. That pressure is 'voltage' [volts] (sometimes referred to as potential). When you start to open the faucet, water flows out. The speed at which it flows is 'current' [amperes] - and any human knows that the more pressure in the pipes, the faster water flows when the faucet is opened (decreasing resistance) - leading to all kinds of fun games as kids. And lastly, you have the volume flow rate: how much total water comes out in a given period of time - and that's equivalent to 'power' [watts] - which, as other's have pointed out, is amps multiplied by volts (i.e. the speed of the water times the pressure).

[IanB]

And lastly, you have the volume flow rate: how much total water comes out in a given period of time - and that's equivalent to 'power' [watts] - which, as other's have pointed out, is amps multiplied by volts (i.e. the speed of the water times the pressure).

Actually no; volume flowrate is "amps". Volume per unit time of water corresponds to charge per unit time of electricity.

Power is something different: it is how much work the pump has to do to move that much water through the pipe. It's a little harder to get a handle on without getting beyond the simple picture analogy and starting to consider engineering concepts.

[IanB]

Just to add: a simple formula for pumping power is (volume flow rate) x (pressure difference), which corresponds closely to the electrical formula of (current) x (voltage difference).

[marmad]

Actually no; volume flowrate is "amps". Volume per unit time of water corresponds to charge per unit time of electricity.

Power is something different: it is how much work the pump has to do to move that much water through the pipe. It's a little harder to get a handle on without getting beyond the simple picture analogy and starting to consider engineering concepts.

This is an analogy - thus not perfectly similar. What I wrote is something invented to describe the basic concepts to lay-persons, and, IMO, the comparison of current to water velocity works better than yours - and I've used it when teaching basic electronics to non-EE students. But, I have to say, when I wrote the above, I was fairly certain that someone would be shortly posting to 'correct' me.

[Excavatoree]

Hydraulic power is proportional to flow x pressure, just as it is with electricity.  (difficult to get the units correct)

At the excavator factory, we must consider mechanical power, hydraulic power, and electrical power. 

[IanB]

This is an analogy - thus not perfectly similar. What I wrote is something invented to describe the basic concepts to lay-persons, and, IMO, the comparison of current to water velocity works better than yours - and I've used it when teaching basic electronics to non-EE students. But, I have to say, when I wrote the above, I was fairly certain that someone would be shortly posting to 'correct' me.

I think I know what you were aiming at, but you wrote exactly this:

And lastly, you have the volume flow rate: how much total water comes out in a given period of time - and that's equivalent to 'power' [watts]

And that sentence, unfortunately, is exactly wrong. I wanted to make sure that nobody was confused when reading it.

I understand you were trying to say that the volume flow of water, when combined with the speed it is moving, corresponds to power, but that was not my first reading and it would therefore probably not be apparent to the student or lay person either.

[IanB]

Hydraulic power is proportional to flow x pressure, just as it is with electricity.  (difficult to get the units correct)

At the excavator factory, we must consider mechanical power, hydraulic power, and electrical power.

This is a much better way of thinking about it as electric current does not really have a concept of speed or velocity.

Getting the units correct is dead simple if you work in SI--but I know that is a foreign concept to many 'mericans 

For example:

Volumetric flow, Q = 10 m3/s
Pressure difference, DP = 5000 Pa ( = 5 kPa)
Power, W = 10 x 5000 = 50,000 W ( = 50 kW)

Compare:

Current, I = 10 A
Voltage difference, V = 5000 V ( = 5 kV)
Power, W = 10 x 5000 = 50,000 W ( = 50 kW)

[Excavatoree]

Hydraulic power is proportional to flow x pressure, just as it is with electricity.  (difficult to get the units correct)

At the excavator factory, we must consider mechanical power, hydraulic power, and electrical power.

This is a much better way of thinking about it as electric current does not really have a concept of speed or velocity.

Getting the units correct is dead simple if you work in SI--but I know that is a foreign concept to many 'mericans 

For example:

Volumetric flow, Q = 10 m3/s
Pressure difference, DP = 5000 Pa
Power, W = 10 x 5000 = 50,000 W

Compare:

Current, I = 10 A
Voltage difference, V = 5000 V
Power, W = 10 x 5000 = 50,000 W

It's not a foreign concept to this one - my company uses SI units exclusively.  I find it amusing to discuss things with clueless vendor sales people.  (what?  millimeters?  What are they?  So, it's 25.4 millimeters, what's that in inches??)

[c4757p]

My concepts of mm-scale distance and hotter-than-ambient temperature have pretty much completely developed in SI. I have no intuition at all for what 20 mil or 150 F are like, but I know exactly what 0.4mm and 70 C are. I think American engineers generally understand SI.

I'm actually starting to get that way with ambient temperature too... 

[IanB]

In oil, gas, refining, power and related industries there is a very strong adherence to lb, ft, F, Btu, psi and related traditional units. While engineers may have no problem with SI units, the production facilities are quite resistant to change.

[c4757p]

How sad.

[MasterOfNone]

Novice: What is the difference between Volts and Amps
Engineer: No that is incorrect. Watt is the product of Volts and Amps
Novice: Never mined my English, what is the difference between Volts and Amps
Engineer:  No I’m telling you for the last time, Watt is the product of Volts and Amps
Novice: You’re so ignorant you can’t answer a simple question
Engineer: Buffoon
<<Tumble weeds <<Tumble weeds <<Tumble weeds <<Tumble weeds <<Tumble weeds

[sleemanj]

Volts = how fast your car is
Amps = how big your car is
Watts = how quickly you can transfer a load of backup tapes across the country

A sports car is a very fast car, there's a lot of volts, but it's also a very small car, there's not many amps.

A station wagon is not a fast car, there's not many volts, but it's a big car, lots of amps. 

The sports car and the station wagon produce about the same watts (they do about the same amount of work), because the sports car can make lots of trips carrying one box full of backup tapes, in the same time as the station wagon can make one trip carrying several boxes of backup tapes.

(With apologies to Andrew Tanenbaum!)

[4to20Milliamps]

First of all (and directed to the original poster), this is a perfectly legitimate question and if you are curious about how things in this world work by all means make observations, study, use all the resources available to you......and never let anyone detract you.

No one, not even that MIT guy with the wild hair was born knowing this stuff, they were taught and made observations and discoveries as they went along.

Part of observing different things is being able to see the unseen, weigh the un-weighed, and measure the unmeasured. There is a system for doing these and it's based on how matter acts under certain conditions and when it does things regularly and with predictable results, they're called laws because the matter always follows these predictable patterns.

here's a good resource example:
http://www.physchem.co.za/extras/units.htm


For me this always an interesting subject and it's based on the very structure of our universe and is the key to understanding a lot of things at a much higher level.....learn all you can you may be the person that changes the world.

Here's something to ponder, the number 39.2



http://books.google.com/books?id=GMkpAAAAYAAJ&dq=water%20maximum%20density&pg=PA426#v=onepage&q=water%20maximum%20density&f=false





http://books.google.com/books?id=ms02AAAAMAAJ&pg=PA202#v=onepage&q=pendulum&f=false

The more you observe, ask questions, and make discoveries the more likely you are to find something that will change the world.

[c4757p]

Volts = how fast your car is
Amps = how big your car is
Watts = how quickly you can transfer a load of backup tapes across the country

A sports car is a very fast car, there's a lot of volts, but it's also a very small car, there's not many amps.

A station wagon is not a fast car, there's not many volts, but it's a big car, lots of amps. 

It works for the mathematical relationship, but I don't care for that analogy because it neglects the physical behavior. Voltage, I think, is best thought of as some sort of "tendency" - the tendency of opposite charges to move back together when pulled apart, or the tendency of water under pressure to push on movable objects, or a number of other more "dynamic" analogies. That's why there's inherent potential energy in a charged capacitor, dissipated power when voltage is lost in a resistor, etc.

[IanB]

Here's something to ponder, the number 39.2

Scientific investigation and experiment is great, but lest the uneducated reader become confused I should point out that the reappearance of the number 39.2 in those two places has no scientific underpinning, it is pure coincidence. Once has to be really careful about seeing significance in details where none exists, since the laws of probability ensure that coincidences may happen far more often than one might naively assume is possible.

[4to20Milliamps]

Here's something to ponder, the number 39.2

Scientific investigation and experiment is great, but lest the uneducated reader become confused I should point out that the reappearance of the number 39.2 in those two places has no scientific underpinning, it is pure coincidence. Once has to be really careful about seeing significance in details where none exists, since the laws of probability ensure that coincidences may happen far more often than one might naively assume is possible.

  are you ABSOLUTELY certain of that?

I will explain the correlation but only after anyone that is curious actually takes the time to do a google search    

I'll give you a clue.....it has to do with molecular bond angles and gravity......good luck.

[IanB]

are you ABSOLUTELY certain of that?

Yes. Absolutely.

I like a good joke as much as anyone, but making jokes at the expense of the uneducated is not much fun 

The reason I am certain of this is that 39.2 in those instances is not a number, it is a measure. Unlike numbers, measures have units of measure, and you can only compare measures if the physical dimensions of the two quantities are the same and if the units of measure are consistent.

For example, 39.2°F is also 4°C, is also 277.15 K, is also 498.87°R. So what's special about the Fahrenheit temperature scale? Well, it was invented by someone who wanted to make sure he would never see negative temperatures on his thermometer in winter (so he obviously never visited Canada or Siberia), and he set 100°F equal to the normal human body temperature (only he got it wrong). So the Fahrenheit temperature scale obviously has enormous physical significance 

What is more, 39.2°F is a measure of temperature and 39.2 inches is a measure of length. In physics temperature and length are entirely different dimensions. There is no unit of measure conversion from one to the other.

So, coincidence.

[smashedProton]

Volts- J/C
Amps-C/S
Watts-J/s-V*A

Hope that helped

[4to20Milliamps]

I like a good joke as much as anyone, but making jokes at the expense of the uneducated is not much fun 

  So you did a search and couldn't find it  are you sure you're using google correctly?


Here's another clue:




http://books.google.com/books?id=AecOAAAAYAAJ&lpg=PA627&ots=yb3i6_uoRn&dq=molecule%20center%20of%20gravity%20pendulum&pg=PA627#v=onepage&q=molecule%20center%20of%20gravity%20pendulum&f=false


http://en.wikipedia.org/wiki/Cubic_centimetre

"A cubic centimetre (or cubic centimeter in US English) (SI unit symbol: cm3; non-SI abbreviations: cc and ccm) is a commonly used unit of volume that extends the derived SI-unit cubic metre, and corresponds to the volume of a cube that measures 1 cm × 1 cm × 1 cm. One cubic centimetre corresponds to a volume of 1?1,000,000 of a cubic metre, or 1?1,000 of a litre, or one millilitre; thus, 1 cm3 ? 1 ml. The mass of one cubic centimetre of water at 3.98 °C (the temperature at which it attains its maximum density) is roughly equal to one gram. Note that SI supports only the use of symbols and deprecates the use of any abbreviations for units.[1] Hence cm3 is preferred to cc or ccm."

I would have to say there is a direct connection.


Here it is again:

"The physicists were very quick in getting the highest purity samples of MgB2 with the highest transition temperature — the temperature at which a material becomes superconducting. Their experiments showed that MgB2 sample pellets containing boron isotopes with an atomic mass of 11 became superconducting at 39.2 K (minus 389 F), while pellets containing boron isotopes with an atomic mass of 10 became superconducting at 40.2 K (minus 387 F). By changing the mass of the boron, the physicists saw a 1.0 K upward shift in transition temperature. "We wanted to understand the mechanism of superconductivity in the material," says Canfield. "And we found that the shift in transition temperature caused by the change in boron mass is consistent with standard models of intermetallic superconductivity."

http://www.eurekalert.org/features/doe/2001-12/dl-omm060502.php


And again:



http://books.google.com/books?id=MncVAQAAIAAJ&dq=emerald%20maximum%20density&pg=PA215#v=onepage&q=emerald%20maximum%20density&f=false