Demos: 5A-14 Electrophorus
The electrophorus works like this. Sulphur has a high affinity for electrons and fur has a low affinity. When the fur is rubbed vigorously against the sulphur, electrons will be stripped from the fur (low affinity) and accumulate on the sulphur (high affinity). Now bring the electrophorus in contact with the sulphur and ground it (touching it) and when you separate the electrophorus from the sulphur plate you will have accumulated a net positive charge on the electrophorus. There is also an acrylic plate which can be substituted for the Sulphur plate but it will yield the same results.