This is a pretty simple question about electric charge flow, but it's something that I just need a clear answer on. So if net charge on a conductor will spread out over the surface (because like charges repel and want to get as far away from each other as they can). But what about for an open circuit without a net charge? Obviously the electricity wouldn't be able to complete a circuit from the positive to negative. Would the positive and negative charges from the power source spread through the wires, or remain at the power source?


2 Answers 2


Power sources don't create charge, they create voltage. Nearly equal and opposite charges already exist in every wire.

The effect of the applied voltage is to push a very small amount of net positive charge on the positive side and negative charge on the negative side. It does this by forcing a very few electrons from the positive side to the negative (these may or may not be "the same electrons" depending on the type of source — it doesn't matter). This flow stops as soon as the force of the unbalanced charges wanting to spread out equals the force exerted by the source.

Within one side of the open circuit, the electrons will distribute themselves according to the electrostatic principles you have already learned.

If you were to disconnect the two wires from the source, then they would have a net positive and net negative charge. It's just so small (assuming the source is not supplying kilovolts) that there are typically no detectable effects.

We usually don't talk about this excess charge in wires, because it is so very small — as soon as a circuit is closed and current flows, far more electrons than that slight excess/shortage flow. But this is exactly the same thing as "parasitic" capacitance of wires, and so it can have a significant effect on the behavior of circuits — it's just not thought of in explicitly electrostatic terms.

If you make the two wires closer together and bigger — make them a better capacitor — then there will be a greater net charge on each wire/plate.


Conductors cannot net store charges of any polarity, so they are neutral but easily give up and accept electrons when excited by some EMF. THese atoms dont actually move at light speed rather create a wave of collisions where charge may be stored in a reactive part such as an inductor or a capacitor.

Inductors store may moving charges and capacitors may store static charges and respond according to the change in excitation available to flow through conductors in a loop.

All insulators are dielectrics with different constants relative to air or a vacuum. The material with the highest dielectric constants are found in electrolytic type caps and batteries and their capacitance density depends on the conductor gap, area and dielectric constant. Electrolytics tend to have the highest charge density near their conducting terminal inner surfaces.

When the dielectrics breakdown due to voltage, it is because the activation energy in the dielectric is reached to freely release electrons like conductors due to very high electric fields in small gaps and results in detonation of material like gas arcs in air with a spark or fuel in a car or dust, humidity and air on the surface of a high voltage insulator (bushing). If there is a vacuum with no particles, then it can withstand extremely high E fields.


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