I would like to know how potential difference is created between two points?Is potential difference created by adding more electrons at one side?If that's the case how to add more electrons at one side?

I'm really looking to know what really constitutes potential difference?

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    $\begingroup$ Read working of battery $\endgroup$ – Anubhav Goel Apr 28 '16 at 0:17

What is potential difference? It's pretty simple, actually.

  • A charge repels other like charges (with same sign). That means, an electron repels other electrons.
  • If you at one point have, say, 10 electrons then they will try to move as far away from each other as they can.
  • This point with many electrons (that is, this point that electrons are strongly repelled from) is said to have high potential. A point of less repulsion is said to have lower potential.

In this way, electrons will always try to move towards the lower potential. In other words: if there is a potential difference between two points then electrons will try to move because they experience an electric force towards the lower potential.

How can such a potential difference be established? That's also pretty simple, actually.

To create and sustain a potential difference you need something to move charges "the wrong way". That is, towards the point of higher potential. You just need a force larger than the repelling force.

  • a battery is a clear example. Inside the battery a chemical process creates such a force which pushes the electrons back up to the higher potential point (the negative pole/terminal of the battery).
  • From this point they again want to move back to the lower potential. They do this by running through the circuit ("around" the battery).
  • When the electrons reach the lower potential, which is the positive pole/terminal of the battery, they are moved back up again on the higher potential ready to travel once more.
  • $\begingroup$ :Could you tell how an electron moves to higher potential even though you have stated that "electron always move towards the lower potential. $\endgroup$ – justin Oct 8 '15 at 9:08
  • $\begingroup$ @justin, Ahh, I see I was imprecise. Corrected now. The point is that the potential difference is because of the electrical forces in the charges. To move anything against the potential difference simply requires a force opposing the electron force. Inside the battery, there are chemical forces doing exactly this, namely working against the electric forces to bring charge the "wrong" way $\endgroup$ – Steeven Oct 8 '15 at 12:10
  • $\begingroup$ :Okay.Could you mention the name of the chemical force?Do you mean to say that there's not only one single force which is provided by the potential difference? $\endgroup$ – justin Oct 9 '15 at 6:02
  • $\begingroup$ @justin The chemical force is just... a chemical force. Just like the electric force is electric force. Just as the charges establish an electric potential difference, in the same way inside the battery a chemical potential difference is set up. When this chemical potential difference causes a stronger force than the electric potential difference, the force is stronger, and the charge will be moved back. What really happens inside a battery is pretty complicated though - something about diffusion and chemical solvents. That would be a new question to ask (or google). $\endgroup$ – Steeven Oct 9 '15 at 6:26
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    $\begingroup$ :Yeah thanks for your comment.I'm not going deeper into working of battery. $\endgroup$ – justin Oct 12 '15 at 5:47

In a circuit, an electric field is created. This electric field forces electrons to move. As current must remain constant (since no charge build up is observed), the electric field must be strongest in the materials that are the least conductive (or most resistive).

As this electric field moves the electrons, they gain kinetic energy. In order to conserve energy, we must therefore say that the potential energy of these electrons has been converted to kinetic energy. Hence, the potential energy of the electron falls. A potential difference in a circuit merely means that work is done on electrons by an electric field as they pass through the circuit and their potential energy changes. Further, we can conclude that since the electric field is strongest in regions with high resistance, the potential difference must be greatest across these regions as well.

This might be a bit confusing since it implies that potential falls in the direction that electrons flow. Since we choose to deal with the flow of conventional current rather than electron flow, potential falls in the opposite direction of current flow.


I will try to explain with some examples. There is never a potential difference when there is equilibrium.

You can think of it as a height difference. Think of positive potential as a high point and the negative one as a low point or ground. So there is a height difference. A thing at the high point is bound to come down.

Similarly, whenever there is charge imbalance, a potential difference is created. I tried to explain as well as I could but the question of exactly how it is created is kind of an abstract thing. It's like asking how the height difference is created between the two points.

Hope it helps.

  • $\begingroup$ :Okay.But I think you could make height difference by standing at a tower from the ground level.Could you tell what's really an high point? $\endgroup$ – justin May 20 '15 at 5:24
  • $\begingroup$ :To increase the potential energy of water flowing down that changes to kinetic energy you just need to increase the height of falling isn't it?Could you explain how would you increase a voltage in the circuit?Is this done by increasing the electrons on one side?If that's the case how could we increase electrons on one side? $\endgroup$ – justin May 20 '15 at 5:48
  • $\begingroup$ You can increase the electrons on one side with an electric motor or generator (based on Lorentz's Law), and you will be increasing the voltage. $\endgroup$ – Guille Jul 24 '15 at 10:46

protected by Qmechanic Aug 29 '16 at 9:04

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