I am building a project that requires a solenoid, but after searching the web I realized that the most underlying problem with solenoids is that it can heat up very quickly. The basic principle of my project is that a solenoid has to actuate when it is cut off but the problem is that the solenoid can heat up if it's connected for too long. I looked around and people seem to be using relays, transistors, FETs, or capacitors to actuate the solenoid.
Is there a way to keep the solenoid in a "sleeping state", meanwhile still supplying current to other components, and then actuate it when the circuit is shut off?
I'm not quite familiar with electronics so I'll just try to guess the solutions. If I use a capacitor, would I basically be making a open/short circuit (sorry, I'm confused with this one, too) to keep the solenoid from being actuated?
What about transistors? How exactly do they serve as switches? If I want the solenoid to be actuated when the circuit is disconnected, or the voltage supply is cut off, how exactly do I make the transistor actuate the solenoid?