Final answer:
A cam-operated valve is kept in its de-energized position by a spring or another type of mechanical force, similar to how a capacitor holds charge or a membrane maintains water pressure.
Step-by-step explanation:
The cam-operated valve is held in the de-energized position by a spring or similar mechanical force. This is analogous to how a capacitor maintains electrical charge after a switch is opened, preventing the flow of electricity, or how a membrane can maintain water pressure when a valve is closed. The spring or mechanical force provides the necessary resistance to keep the valve in its default position until it is actuated by another force, such as a motor or a solenoid when it is energized.