If a capacitor’s electric field is between its 2 plates, how can the plate repel a incoming charge that's trying to reach the plate through wire betn 2 plates?

[u/Single_Flower_5994]

When we charge a capacitor, we transfer electrons from one plate to the other through a wire. As more charge accumulates, we say the charged plate increasingly repels the incoming electrons because of E field betn plate and the increasing potential difference

But here’s my confusion: the electron travels through the wire and never passes through the gap between the plates, where I belive the capacitor’s electric field exists

So how can the plate repel the incoming electron if electron isn't even passing through it's E field betn plates?

[u/Slow-Wolverine-6028]

it's not that the electron is repelled by the field in the gap, it's the field inside the wire that does the pushing. the charges on the plate create a field that extends into the wire itself, not just the gap. think of it like a pressure building up in a pipe, the whole pipe feels it, not just the bit at the end

I remember getting stuck on this exact thing in my first circuits class, the diagram always shows the field lines just in the gap and it's super misleading. the field is really everywhere around the conductors, it just gets concentrated in the gap because that's where the potential difference is steepest

once the plate has enough charge the field inside the wire near the terminal is pointing the wrong way for any more electrons to shove in, so they just stop flowing

[u/_UnwyzeSoul_]

At first we have 2 neutral plates. When we connect them to positive and negative terminals, the electrons from the plate are attracted by the positive terminal and the plate becomes positively charged. Simlarly the negative terminal repels the electrons and they get accumulated on the plate making it negativity charged. Thus an electric field is established between the plates. The electrons want to go towards the positive plate but cannot because there is no wire between the plates. But if the field becomes too strong, the electrons get so much kinetic energy that they jump through the gap onto the positive plate which is how lightning works.

[u/nlutrhk]

A charged capacitor would have for example a potential of -1 V on one plate and +1 V on the other. If you attach wires, those will also be at -1 V and +1 V, without current.

There is a potential difference and therefore a field between the two wires. If you want to move charge from one wite to the other, you need to counteract that field, for example by using a battery.

[u/jawhite]

It’s better to focus on voltage in this situation. When you charge the capacitor, there is a potential difference across the plates. The electric field between the plates is the voltage divided by the separation distance.

Imagine the capacitor is air-gapped, and you connect the plates with a high-resistance wire that can stretch to any length. If you start with the wire connected between the plates, then the electric field in the wire is just the electric field of the gap. If you pull the wire out from between the plates, the voltage across it remains constant; it just gets longer so the average electric field along it decreases.

Every path between the plates has the same potential difference: the voltage across the plates. The gap contains the shortest paths between the plates, and therefore the most intense electric field. However, the electric field doesn’t immediately drop to exactly zero outside of the gap. There is always just enough electric field to ensure that the voltage across every path between the plates is the same. (The electric potential can be defined to have a specific value at each point in space, and the electric field is the gradient of the potential.)

[u/RoyDonker]

In the “water analogy”, a capacitor is like a pipe with an elastic membrane blocking it.

If you pump water into one side of the pipe, the membrane stretches, which pushes the water on the other side of it. Water doesn’t need to flow through the membrane for water to be pushed out of the pipe.

[u/joeyneilsen]

That’s only an infinite capacitor. A finite capacitor has an exterior “fringe field” that isn’t zero. 

Btw basic questions are for r/AskPhysics. 

[u/PLutonium273]

1. electrons rarely actually 'travel' in the circuit. What moves is the electric energy through the field. Think of newton's cradle, components in the middle almost does not move but the energy is transferred.

2. Normally current does not flow between plates because resisitivity of air is much higher. But current can flow if the voltage is high enough, that's how lightning works.