Electric fields

Every electric charge sets up a field in the space around it — an invisible influence that would push or pull on any other charge placed nearby, even before that other charge actually arrives. The field is a property of the source charge, existing whether or not anything is there to feel it.

Field strength falls off with distance from the source, so a charge placed closer to another charge feels a stronger push or pull than one placed farther away. Crucially, the field at a given point doesn't depend on the size of whatever test charge you use to probe it — a bigger test charge feels a bigger force, but the field itself, force divided by that test charge, comes out the same either way.

Field lines are a useful drawing convention for visualising all this: they point in the direction a small positive charge would be pushed, and where they bunch closer together, the field is stronger. They're a map of the field, not a set of tracks that a charge is somehow forced to follow.