P.17.....Perhaps you will want to ask , what is an electric field? Is it something real, or is it merely a name for a factor in an equation which has to be multiplied by something else to give the numerical value of the force we measure in an experiment?
Two observations may be useful here.
First, since it works, it doesn't make any difference. That is not a frivolous answer but a serious one.
Second, the fact that the electric field vector
at a point in space is all we need to know to predict the force on any chage at that point is by no means trivial.
It might have been otherwise! If no experiments had been done, we might imagine that in two different situations in which unit charges experience experience equal force, test charges of strength two units might experience unequal forces,, depending on the nature of the other charhges in the system. If that were true the field description would not work.The electric field attaches to every point in a system a local property, in this sense: ifwe know E in some small neighborhood, we know without further inquiry, what will happen to any charge in that neighborhood. We do not need to ask what produced the field.