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Old 24-10-2009, 20:27   #106
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Not to put too fine a point on it.
Not Sure is, well, not sure and willing to argue his right to be not sure.
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Old 24-10-2009, 20:45   #107
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Notsure,

Look at it this way. I try to use this example to explain volts and amps to non technical friends.

Compare electricity to water.

The pressure of the water in a pipe or psi is like the voltage. Voltage is a way to measure the pressure of the electricity.

The amount of water that flows out of a pipe is like the amps or current that flows out of a wire (or solar panel or battery).

So consider this example.

You want to fill a swimming pool with water (or a battery with electricity)

If you fill the pool from a pipe with water under 1000 psi it will flood the pool. Well not if the water pipe is only as big around as a soda straw. A case of a lot of pressure but not much water (or in electrical terms, a lot of volts but not many amps so not much total power).

On the other hand, would you flood your pool if you tried to fill it with a water pipe with only 5 psi? Well if that pipe had a 10 ft diameter and was connected to a large resevoir then yes you would.

Your lightening bolt example is equivelant to a 10 ft pipe AND 1000 psi.

For the other engineers out there, I know the analogy isn't perfect and I am playing loose with some of the details but it's close enough for those that don't understand.
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Old 25-10-2009, 06:41   #108
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I think most readers will grasp the pipe & pool example, so I'll try to add resistance and voltage drop:

If you put a valve into the pipe at the end of the pool and close that valve, the pressure inside the pipe will be the same in the whole pipe. This is much like the open voltage of a solar panel.

Now, if we open the valve, water starts to flow and the pressure will change. The pressure at the start of the pipe (where the pump is) is higher than at the end, just before it dumps into the pool. The longer the pipe, the bigger the difference and the smaller diameter of the pipe, the bigger the difference. Just like the voltage drop over an electrical wire.
The reason is the friction between water molecules and the inside walls of the pipe. As the pipe gets smaller diameter, the higher percentage of water molecules touch the wall.

Last step is a partially closed valve halfway. The pressure in front of the valve is higher than after the valve. Also, the rate of water flow is reduced. This is much like adding a series-resistor into an electrical circuit. The pressure-loss between start- and end- of the pipe can be found "over" the valve, just like the voltage drop can be found over the resistor.

The solar panel can be represented as the pump plus a partially open valve connected directly to it's output. The valve is the internal resistance.

ciao!
Nick.
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Old 25-10-2009, 06:51   #109
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Nice, thanks for taking the time to write that up.
Can't say I completely understand it all, but I do believe you when you say, IF I took the time to, I could understand most of it ;-)

I like the water to electricity analogy of course cause it easy to understand... but one thing is important... water no shock you like electricity does!!!
The thing is, some people just want to be right, no matter what the facts are. They will argue it unto death, and believe it no matter what. Just ask any high school teacher!

Bob
Bob
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Old 25-10-2009, 07:08   #110
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Bob,

They cut steel with water so I guess that it's just a question of how much pressure/voltage ;-)

cheers,
Nick.
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Old 25-10-2009, 07:51   #111
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Quote:
Originally Posted by s/v Jedi View Post
Bob,

They cut steel with water so I guess that it's just a question of how much pressure/voltage ;-)

cheers,
Nick.
Yeah good point. Saw that on a show where they cut the steel with water...
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Old 29-10-2009, 10:59   #112
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Pearls before swine!?


In all seriousness. I have learned more about practical electrical circuits from Nick and Rick than I ever learned in Chem and Electronics.

Thanks and a deep bow. It is most appreciated, by many!
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