Now the circuit has been altered:
What will this circuit do after we have connected it to the "juice"?


Oh - of course nothing at all will happen (as the situation at the beginning is not drawn)!
As long as there is no current there will be no contact between A and C, and thus no current will feed the magnet.
Now we "help" the relay by pressing down the contact by hand (or switching-on the current for the coil by another switch bridging the interrupted relay contact).
Now it is magnetic - pulls down the contact - and will provide itself with the current!
It will remain magnetic until we interrupt the current at another place or switch it off totally!

This effect could be used to build an intrusion alert.
Would it as well be suitable to store a binary state?


move on