Two students conduct the following experiments and come to different conclusions.
Experiment 1: Student A rubs a glass rod with silk then hangs the glass rod by a string. The end of the rod attracts a plastic rod that is rubbed with fur.
Experiment 2: Student B rubs a glass rod with silk then hangs the glass rod by a string. The end of the rod repels a second glass rod that is also rubbed with silk. Student A hypothesizes that there are two kinds of electricity.
Student A reasons that friction between some types of objects produce positive electricity while friction between other types of objects produce negative electricity.
Student B hypothesizes that there is just one type of electricity. Student B reasons that neutral objects have equal amounts of positive and negative electricity, and that friction between neutral objects will separate the positive from the negative.
Student B’s hypothesis is a restatement of which fundamental physics law?