Tuning Capacitor (5C10.35)
/Tuning_Capacitor_(5C10.35).jpg)
Similar to the Parallel Plate Capacitor (5C10.20), but this is a large version of the tuning capacitor used in AM radios, in which the area (overlap) between the plates can be changed.
Use the red acrylic rod and wool to charge the red positive terminal. Rotate the plates to change the plate overlap area.
/Tuning_Capacitor_(5C10.35)_2.jpg)
/Tuning_Capacitor_(5C10.35)_3.jpg)
/Tuning_Capacitor_(5C10.35)_4.jpg)
Note that electrostatic demos are sensitive to room humidity. While this demo works most of the time, during summer the capacitor's charge can dissipate at a rate such that the voltage drops to 0 in less than one minute.