# Flow of water and flow of electrons, how this analogy works?

If flow of electrons analogy can be imagined as flow of water, how to imagine electricity, that comes in this whole picture?

When plug from bottom of sink is taken out, gravity pulls water molecules, creating pressure difference, in sink there is larger pressure than in open hole, making water to move to place, where is less pressure, until pressure is equal in all places, water can flow.

As I have understood, electricity is some field around each electron. Power of field is called electric charge, mesured in columbs, every electron has some charge, eaven those, who are sitting tight, that is called static electricity? That charge is generated when electrons rub/hit against each other, when they are "made to move", when electrical potencial, or pressure difference is made, by connecting to medium, another medium, that has... What that connected medium has, that makes electrons flow? Less electrons? Less electrons with electric field around them? If that is field, that can have some maximum ammount of charge, can charge vary, how that affect flow? I don't think, it can be explained with water, as water isn't carrying... anything...

What is mesured in amperes? What is rate of flow, is it a speed of water/electrons flow?

Are electrons same as water, in manner of, they are just some sort of matter, that is flowing in another medium, but water has much larger particle size, so its hard to make is analogy in my mind - there is no medium, in which water can flow, water is medium by itself.

If I forget, that water is medium, but pretend, that water can only flow in... air, places where air can go in... Then how does wire connections work? If There is one wire, that divides in two, as some sort of connection, does in each wire, goes same ammount of electrons (if we pretend ideal/same conditions in both wires)? Does that mean, there will be half of electrons in one wire, and other half in another wire? The more wires I connect, the less electrons will be in each wire? If one of wires will have damaged lattice or resistor sitting middle of it, will electrons "run way back" to connection place and go into other wires, where is less resistance or they will stay at same place, just building up pressure, constantly making denser electron cloud in resistance area... Ehh...

I know, I'm asking too many questions, that touches too many sides of electricity, but please, I want some analogy explanation, that would allow me better understand this whole "stuff". :) Maybe, someone can suggest some visual materials (video, pictures), for this?

-

To begin with, a good physical analogy matches physical quantities of one system to physical quantities of another system that act mathematically equivalent in some (limited) context.

The example of electric current (Amperes C/s) and electric potential (Volts or J/C) makes a good comparison to water flow (kg/s) and gravitational potential (J/kg). However, in order to use this comparison, you need to back off from the concept of pressure, as well as a few others. Consider a lazy river type situation where a pump imparts the gravitational potential to the water and allows it to flow through the resistance of the rest of the closed loop, and maybe a water wheel.

Alternatively, you could consider a loop of water employing the analogy with quantities of flow (kg/s) and hydrostatic pressure (J/kg or psi or many other units). An example of this could be something like a flow loop in a nuclear plant, for instance. There exist components that impart pressure to the flow, then there are components that have friction (again, like a resistor) that balance against the work of the pump. The reason this might not be as good of an example is because it requires a pressurized loop, which is further from our common everyday experience.

It is true that the water does not exist in a medium in the same way the electrons in an electric circuit do. This is just one of the many many reasons why the analogs are not perfect. The thing to focus on is that the equations can be the same with different quantities in place. Right now, I'm focused on the most simple laws possible. For instance:

$$V = I R$$ $$P = I V$$

The examples I discussed before can certainly be put in terms of these laws. All that these do is illustrate a case where there is a flow with a unit attached to it, and that flow has a per-unit energy value which dictates how much flow will occur over static components (the resistor case) and then concepts of power (among others) come naturally.

-
Thanks, that is almost the answer, I was waiting for :) –  Deele May 25 '11 at 15:37

Picture this, A tank of water with a valve at the bottom, and a hose attached to the valve. The tank represents a battery, the valve represents resistance, and the hose is the wire. If the tank is on the ground and the valve is wide open water will flow through the hose, but instead of water picture marbles. If you raise the tank up high, the water will flow faster, representing more voltage (higher tank) and more current(faster flow). Okay, you can put the tank down now. Close the valve half way, that represents higher resistance. Half the rate of flow comes out the hose. Raise the tank, and more water flows, but at half the rate as before. Now picture a "Y" fitting with a valve on each split. Shut one valve off and run water through it. The water up against the closed valve can't go anywhere so it just sits there waiting for the valve to open. When the valve opens, some water flowing out the other open valve flows through the newly opened one. Open both valves halfway, equal amounts flow out of each. Now close one 3/4 of the way more water flows out of the one that's half way closed. One more point, the bigger the hose the more water can flow, the bigger the wire the more current can flow. And remember, unplug it before you work on it.

-
I recommend You try this "theory" in experiments. –  Georg May 27 '11 at 9:35