A parallel-plate capacitor is a device used for storing energy. When the 20.0V battery is removed, it will discharge and release that stored energy in the form of voltage spikes or radio waves. Typical parallel-plate capacitor circuits are used in CRT monitors, radio transmitters and receivers, TV sets (including microwave ovens), radar systems. A typical circuit has a resistor to protect the device from overloading when high energy surges occur.
The discharge of the stored electricity is not harmful because it dissipates quickly through its two large flat plates that have very little resistance between them. The charge on each plate diminishes as time goes by but does not go away completely until there’s no more voltage available for charging either one or both of those plates with new charges. This continues until they reach zero volts per side meaning neither anywhere near enough power remains to cause any future spikes detectable above background noise levels. On the other hand