# Basic electricity question

• posted on November 21, 2005, 5:05 am
We all are familiar with the analogy about the flow of electricity comparing with the flow of water: voltage being the water pressure in the pipe, amperes the measurement of how much is passing through the
pipe, and ohms being the size of the orfice. Using the water analogy, what is wattage? I know my name is Einstein and all that, but hey. I don't know everything.
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• posted on November 21, 2005, 5:21 am
Gomer Einstein wrote:

How much of a machine the stream of water could drive if it were directed through a turbine wheel.
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• posted on November 21, 2005, 11:25 pm
Wattage = Hot Water
--
Coasty

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• posted on November 24, 2005, 3:49 am
On Mon, 21 Nov 2005 18:25:46 -0500, "Coasty"
wattage can be compared to capacity measured in gallons per minute. This is the simplest (but not technically) the best analogy. Hope this helps you understand.
Sparky P.S. By the name you can probably guess my occupation.
Thats right>>>>>>>electrician
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• posted on November 24, 2005, 6:52 pm
wrote:

You have to remember that beyond a certain point the water analogy just doesn't "hold water"
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• posted on November 24, 2005, 6:57 pm
I tired using water all through electronics school. some things worked well some things didn't
wrote:

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• posted on November 25, 2005, 2:14 am
Coasty wrote:

I think Coasty is probably as close to an answer as you can get. I am not an expert--BUT--(you KNEW I was going to say that)--in electricity, power is equal to amperes times the square of the resistance in the circuit. In your example, the smaller that little orifice is, the higher the resistance is. I think that the power in watts is just a number. But in a circuit with resistance in it, the power has to be dissapated somehow. With resistance heat is given off. In this example, heat is also given off. But I don't think very much. First of all, water doesn't compress very much. Second, there would not be much friction going through that little orifice.
In other words, I don't think you could appreciably increase the water flow above a certain rate, no matter how much pressure you had. This is different than electricity. The current is directly proportional to the voltage.
Thoroughly confused? The electrons always know what they are doing -- and they will always react the same way to the same set of parameters. So it is the way that we visually or verbally try to describe what is happening that is a source of confusion.
Jim
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• posted on November 25, 2005, 12:10 pm

The analogy between water and electricity in theory has some of the same aspects in analogy only. The actual performance has similarities but the affects are totally different.
It is like comparing apples to oranges, both grow on trees, growth based on sun, water and soil conditions and that is where the similarities end. One is a northern crop the other a southern crop, they taste different, they have different skins, the interior of the fruit is structured different.
You can use comparative analyses to almost anything however, it is just that. It has no real basis on theories or actual results. You can't power a TV with water or drink a glass full of electricity, you can eat an apple or an orange, so water is closer to apples and oranges that it is to electricity.
Sparks may be an electrician but he is not a hydrologist.
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Coasty
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• posted on November 29, 2005, 10:27 am
Since the original poster's question was pertaining to the actual water analogy, I like the first response best, which I think speaks to the actual 'brute force' (power) of the water coming out of the pipe, and "how much of a machine it could drive if it were directed to driving a turbine wheel." The whole thread is a good illustration of how important it is to use the proper size wire, etc for your application.
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• posted on November 26, 2005, 12:00 am

You're right, Jim. Same thing is true for air flowing through tubing and an orifice or nozzle - when the flow reaches the speed of sound in the fluid (liquid or air), the orifice chokes and maximum flow rate (equivalent to wattage in the electrical world) has been reached. I don't think there is an electrical analog to choking flow, except that as the flow through a resistor increases withour limit the I squared R heating would eventually burn out the resistor and stop the flow, which is not the same thing as choking.
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• posted on November 23, 2005, 9:16 pm
On Sun, 20 Nov 2005 23:05:59 -0600, snipped-for-privacy@webtv.net (Gomer Einstein) wrote:

CFM