# 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?

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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.

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