How well can water illuminate electricity

whiteoxe

Can you use a exact water analogyto demonstrate resistors in series and parallel ?

say your + battery wire/hose was 12V and you had two 'resistors/blocking taps' in series and the 'resistor/taps' were half open blocking the flow by 10ohms/pressure units for the first 'resistor/tap,'

then the second 'resistor/tap blocking' the same amount as the first, then the total blockage in the wire/hose would be 20 ohms/units.

Would the wire/water hose still have 12V pressure coming out the end after passing through
the two resistor taps ?

and what woulcd happen if the two 'resister taps' were even tighter , 20 ohms/pressure units ?

and also what would be happening to the ' water volts' if there was a small 6volt capacitor in the circuit and a 3 volt LED ?

I thought maybe another water analogy would help me, but there is likley a better way of expressing the water and electricity than i managed.?

I didnt get to the parallel part of the question, maybe tomorrow

W9GFO

whiteoxe wrote: »

Can you use a exact water analogyto demonstrate resistors in series and parallel ?

Exact? No. The water version would need to be a closed circuit so a pump would act as the battery. With electricity all the voltage has to be dropped by the end of the circuit. In a water system I don't think that is true. If you put restrictors in series the first one would have more impact than the following, especially if the first is a higher value.

We have a 9 gpm restrictor on our well. I doubt that if I added another one that our flow rate would be reduced to 4.5 gpm. However I do think that if we paralleled another 9 gpm restrictor we would get 18 gpm.

whiteoxe

If I had a fairly large capacator in a small circut on a breadboard(i dont have any right now) and a LED, when i turned it on could there be a small delay beforde the LED turned on. I'm thinking the capacitor needexs time to charge up then it reales the current ? I would try it now if i had the parts, I'd try all sorts and sizes of capacitors.

Mike Green

The water analogy does work. Here's a nice website that has illustrations of the relationships.

xanadu

whiteoxe wrote: »

If I had a fairly large capacator in a small circut on a breadboard(i dont have any right now) and a LED, when i turned it on could there be a small delay beforde the LED turned on. I'm thinking the capacitor needexs time to charge up then it reales the current ? I would try it now if i had the parts, I'd try all sorts and sizes of capacitors.

You can always simulate! http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capchg.html

Dr_Acula

@Mike Green- great link there. Has me thinking about capacitors and inductors now as well...

Re the original questions:

Can you use a exact water analogyto demonstrate resistors in series and parallel ?

Yes. It works pretty well actually. Assuming you understand water and pumps of course!

say your + battery wire/hose was 12V and you had two 'resistors/blocking taps' in series and the 'resistor/taps' were half open blocking the flow by 10ohms/pressure units for the first 'resistor/tap,'

then the second 'resistor/tap blocking' the same amount as the first, then the total blockage in the wire/hose would be 20 ohms/units.

Correct. Resistors add in series. So do taps.

Would the wire/water hose still have 12V pressure coming out the end after passing through
the two resistor taps ?

Ah, no, the pressure would be 0V, or very close to it. It started off with 12V of pressure, when it got through the first tap it was reduced to 6V of pressure, and now as it comes out of the second tap it has virtually no pressure left. It still has flow (which is current) but no pressure.

and what woulcd happen if the two 'resister taps' were even tighter , 20 ohms/pressure units ?

V=IR The V is the same, R is twice so I is halved. The flow would be halved.

Fun, isn't it!

Ok, have you even turned off a tap quickly and heard the pipes bang? That is because the flow kept going and the pressure went up very high. Take a big pipe, you can have it laid out straight or coil it, and run lots of water through it. That is an inductor. Now suddenly turn off the flow. The pressure goes up. This is how switching regulators work, and how you can feed in 12V into a coil and get thousands of volts out to make a spark for a spark plug.

Capacitors. This is where I get a bit confused myself. Instead of the battery being a pump, instead it can be a tank on top of a hill. Run a pipe down to the bottom of a hill and a tap. We have lots of volts (pressure) and no flow. Now run a large pipe back up the hill. Turn on the tap and start filling the pipe. The volts (pressure) goes up. That pipe is the capacitor. Its diameter is its capacitance. Eventually the water reaches back up to the tank level and it stops filling. The rate at which it fills (through a constant resistance) is the familiar RC curve.

Re your last question about the led and capacitor, what is the circuit? If the capacitor is in parallel with the LED and you are driving the led with a resistor, and the capacitor is large, then yes, it will take a while for the LED to come on.

One thing about water vs electricity. With water, it can take weeks to build pumps and tanks and pipes to test things out. Much quicker to plug capacitors and resistors into a breadboard!

Heater.

We can model a capacitor easily. Just put a rubber membrane across the diameter of the pipe. Now water cannot actually travel all the way though the pipe. The membrane blocks the way. But that membrane can stretch so the water in the pipe can move a bit one way and a bit back the other way. That is to say a direct current (DC) is blocked but an alternating current AC can exist in the pipe.

There is a nice animation of this on this page http://en.wikipedia.org/wiki/Hydraulic_analogy which explores this whole water analogy topic nicely.