The night before an exam, your study partner asks what you can do to a parallel-plate capacitor to avoid the problem of the electrical breakdown of air. You answer that a nonconducting dielectric material can be inserted. Your friend is confused as to why other things wouldn't work. Why wouldn't it help, for example, to add a conducting slab? Why isn't increasing plate separation also a valid answer? After all, moving charge carriers very far apart must decrease their effect on the air between them. Why do these alternatives not work?