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FrozenGate by Avery

Ok, yeah...but why?

scumbagatheist

scumbagatheist

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Feb 10, 2013
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So, I get and understand that in a parallel circuit total parallel resistance is less than any one of the individual branch resistances, because parallel resistors resist less together than they would separately.

But...why? Why do parallel resistors resist less? I cannot seem to find an answer.

No, this is not a trolling question.
 





If no one answers by time I get home to my pc I will explain it for you - I'm not going to type it on my phone, haha.
 
The total resistance is less because the current is now spread among multiple current paths. Think of the parallel resistances like having more pipes that water can flow through. Using two pipes will always provide additional flow compared to just one of the pipes. The same thing with current.
 
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^ yep.

The analogy that was used when I was learning these things is as follows:

Say you have a one way road just wide enough for a single file line of cars. The cars are bumper to bumper the whole length of the road and there is a backup of cars trying to turn in to that road from an intersection. Now add a second road (or lane) parallel to the first road. Now twice as many cars can turn on to that road. The higher the resistance the fewer cars can fit on the road, the more backup there is. The resistance is how long each car has to wait to turn on to the road. Add another path in parallel and you cut down how long each car has to wait.
 
It's interesting how water can be used to visualize pretty much any electrical circuit. You can think of voltage as the water pressure, current is the volume of water, you could think of resistors as different size pipes, capacitors can be tanks, transistors valves, inductors can be blocking off a piece of pipe quickly while water is flowing through it etc.

So in terms of water, you could think of a voltage regulator as a pressure regulator, and a current regulator as a volume regulator.
 
That only works when the person has an understanding of basic plumbing principles though. Many times I have tried the water analogy only to have the student reply with "but how does water work?!".

It is a shame but most people in this world never once question how water comes out of their tap or what makes their lightbulb (or computer!) work.

I once met a guy who didn't understand why you put gasoline in your car tank but it never comes out of anywhere, and keeps needing more!
 
Thank you all for the analogies. That was all I needed. Sometimes I have trouble thinking in the abstract. Give me a little bit, I'm actually getting this stuff. I just need more time.
 
There are some pretty direct analogies between the two domains.

As for inductors, I think a more appropriate characterization would be an inline flywheel. They resist turning because of their rotational inertia, but by the same token force the current/water to continue moving if rotating.
 
Only thing id change, current is like the water speed and watts would be volume. That way it pretty much follows ohms law. Like with a constant pipe size changing pressure changes speed and the result of pipe size, pressure, speed can tell you the volume, etc.

Its still not perfect but fairly close.
 
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Watts being volume?? That's crazy talk! lol...Aren't watts the measurement of the work done by the volume of flow?? In keeping with the metaphor, watts would measure the speed of the water wheel attached, wouldn't it?
 
Watts are power which would be total water flow (volume). You could change some of that power into other forms, like spinning a water wheel. The spinning wouldn't be the actual power though. Thats like measuring a laser at 1W then saying it takes 1W to run.
 
Well, either way, we have The Law of Conservation of Energy in Physics. Just so I know where all that work is going: output in watts, watts of heat dissipation, etc...
 
In the water analog it would be friction, in an electrical setting it is resistive heat and radiative losses.

Conservation of energy is ALWAYS preserved, sometimes where it goes is not so clear though.
 
That's funny from you, Dave. I picture you, slaving over something, until you have every variable accounted for.
 
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