To illustrate charging by induction.
Van de Graaff generator, electroscope, and two metal plates with insulating handles.
Run the Van de Graaff for a couple of seconds to develop a small charge on the dome. Hold the two plates touching each other near the dome (but do not draw a spark) with one closer to the dome and one further away. While the plates are near the dome, separate the two plates and then remove them from the area of the dome. The two plates will be equally but oppositely charged, as can be verified using the electroscope.
Oleg Jefimenko, How can An Electroscope be Charged This Way?, TPT 56, (1979). ◙Charging of an Electroscope, Little Stinkers, Phys. Teach. 3, 185-186, (1965). ◙Lecture Demonstrations Note Sheet: Directions for Electroscope Induction.