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I’ve been doing much research the last couple of days about electricity. I have a pretty good understanding of Watts, Joules, Coulombs, Amperes, Ohms, and I know Ohms law finding voltage and all and I understand that Volts measure the electric potential between to points on a circuit and that Volts are the “pressure” force that push the electrons through the circuit.

What I can’t seem to understand is how to know what creates that “pressure.” Is it based on how many free electrons are on one side of the lightbulb, for example, compared to the other? Can you create more voltage by loading more electrons into one side?

I understand there isn’t a simple answer to this question so posting any article links or video links would be what I am looking for.

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  • \$\begingroup\$ Do you know about electric field? \$\endgroup\$ – The Photon May 8 '19 at 1:35
  • \$\begingroup\$ @ThePhoton not really. I know that it is involved and that it’s part of the 3 fields like gravitational field, magnetic field and electric field but that’s all I know \$\endgroup\$ – Timinycricket May 8 '19 at 1:46
  • \$\begingroup\$ @Timinycricket There are far more than three fields. \$\endgroup\$ – Hearth May 8 '19 at 2:15
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So, what you missed in your list of things you understand is electric field.

From Maxwell's equations, we know there are two ways to produce electric fields. Either by the presence of electric charge, or by changing magnetic fields. Lets ignore magnetic fields to begin with and talk about charge.

Every positive charge produces an electric field radiating away from it. Every negative charge produces an electric field radiating towards it.

In the presence of an electric field, a positive charge experiences a force in the same direction as the field. In the presence of an electric field, a negative charge experiences a force in the opposite direction from the field.

Because there is a force on a charge in the field, moving a charge around in an area with nonzero field requires either doing work on the charge (increasing its potential energy) or having work done on you by the charge (reducing its potential energy).

Now we get to voltage. Potential difference, aka voltage, summarizes how much work it would take to move a 1 C charge from one place to another in a particular electric field.

So really, it's not the voltage that pushes the charges around in a circuit, it's electric field. But using voltages we can calculate the net effect of those fields without having to keep track of what the field is at every point in the circuit.

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  • \$\begingroup\$ Ok that does help me make some sense of it. So the more charge in an area the more voltage? Which is why transformers can step up or down voltage based on how many turns? Because the tighter together the stronger the field? \$\endgroup\$ – Timinycricket May 8 '19 at 4:59
  • \$\begingroup\$ Near a positive charge will be a high voltage. Near a negative charge will be a low voltage. To explain a transformer we have to go back to the other source of electric field: changing magnetic field. \$\endgroup\$ – The Photon May 8 '19 at 5:03
  • \$\begingroup\$ okay I guess I still need to dig into the electric field to get a better understanding of what you’re explaining \$\endgroup\$ – Timinycricket May 8 '19 at 5:11
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Is it based on how many free electrons are on one side of the lightbulb, for example, compared to the other?

Sorta-kinda, but I think it's more valid to think of the electrons as an incompressible fluid, like water in a pipe, and whatever is generating the voltage (i.e., a battery) as a pump.

Can you create more voltage by loading more electrons into one side?

Yes, but that makes more sense if you're working in high-voltage low-current stuff like electrostatics -- not the kind of things that make ordinary lightbulbs light up.

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