# What really happens in a electric circuit?

How do electrons behave in an electric circuit? There was a question before about a voltage drop which was interesting, but I can not participate in that discussion, so I am writing this question hoping to clarify this topic.

Electrons in a wire behave like an incompressible fluid. Driven by the potential difference, they all must move at the same time so they all gain energy instantly and then they all lose this energy due to moving through a specific resistor (like a wire itself).

For example, when you turn on the light, it starts glowing instantly although electrons are moving very slowly, but like cars in a row in front of a traffic light they all feel the signal to move so they start moving.

Suppose it is a battery that is making them move. If it is 1.5 V battery, it means that each unit of 1 C charge gets about 1.5 J. Not in the battery, but anywhere in a circuit. Electrons get what we call a drift speed; now they are moving slowly through the wire (1 cm/s) so there is no way that electrons from negative terminal are those we have to wait for, oh no!

Almost instantly, the influence of the field of the battery is spread through the wire. All electrons move now. Even if there is no resistance, electrons must come to positive terminal and sink in. And when they do, we say that they spent their energy, like a ball falling from a high building. This is a short circuit and it drains battery very fast since without any resistance, the current gets very high. When you put a light-bulb or a hater in this circuit, it will converse this energy of the electrons into light or heat or something.

So electron are entering and giving their energy away, then moving further, going to the positive terminal. They are slowing those electrons behind and a constant current is established in a very short period of time.

Knowing all of this, the question is, how do we have that the sum of voltage drops is always equal to a voltage of a source? Is the energy spent in a light-bulb equal to the whole energy of charge carriers? I should say not likely?

• you missed one, i wrote: so electron are entering, and it should be, electrons...plural. Commented Nov 11, 2014 at 16:17