Explaining “Electric Field.”
It starts with the notion of “opposites attract and likes repel.” A positive charge, such as that on a proton, will attract a negative charge, such as that on an electron. By the same token, two positive charges will repel each other.
There are two rules that come from physics and that establish the meaning of “electric field.” The first rule is that a charged particle will create around itself an electric field. The second rule is that a charged particle that finds itself in the presence of an electric field will feel a force. But what is happening is that the charge that created the field is either pushing or pulling the charge that wandered into its neighborhood.
Suppose your friend put a metal ball on an insulated stand in the middle of a room. Suppose he found some way to impose a positive charge on the ball. Don’t ask me how he did it, just let’s presume it is done. According to Rule One above, there will be an electric field surrounding that ball. But let’s ignore that rule for a moment. In fact, your friend covered the ball with some type of insulating cloth, so that you did not know that large, charged ball was in the room.
Now suppose you walk into the room, holding in your hand a smaller metal ball that also has a positive charge imposed upon it. I suppose you would need to have insulating gloves on, to keep the charge from leaking out through your hand. Stand at some spot in the room. You may be surprised to feel that ball in your hand being pushed by some unknown force. Hold the ball tight, so that you don’t lose it. Move to another spot. You still feel the force that something is using to push the ball in your hand. But now the force is in another direction, and it doesn’t feel like such a strong force anymore. (I know that that means you have moved away from the bigger ball in the center of the room, but you do not see that other ball, and do not know it has anything to do with the force you are feeling on the ball in your hand.)
Move to many different spots in that room. Sometimes the force feels stronger, sometimes it feels weaker. It is always in a different direction, however. If we were to uncover the large ball in the middle of the room, and let you see it, and let you figure out that it is the source of the pushing, you may discern that no matter where you are in the room, the direction of the force is such that the ball in your hand is being pushed in a direct line away from the ball in the middle of the room. That is why when you move around the room, the direction of the force changes.
That is the notion of an “electric field.” Depending on your location with respect to the source of the electric field, there will be a stronger or weaker force being imposed on the charged particle (i.e., the metal ball in your hand). It is a “field” in the sense that no matter where you are, the charged particle in your hand is going to feel a force. It is also a “field” in the sense that the direction and strength of that force will depend on your position within the room.
One final note. In a capacitor, the charge is not on a ball in the middle of the room. The charge exists on each of two parallel plates. So the direction of the force that an electron might feel, if it were to be placed in the middle of the two plates, would be in the direction of one plate towards the other. That is the reason that we speak of there being an electric field between the plates.
