Question

a security system uses sensors at every door and window which will set off an alarm if any one of them is opened. there is also a keypad by an entry door to turn on or turn off the system. describe how these components can be wired in a combination circuit to provide the needed security.

Answer 1

Wire the motion sensors in rooms and in between rooms in a series circuit and connect the sensors on all the doors and windows in a parallel circuit.
The reasoning being, if you open a window or door the sensors will trip and the circuit will break if the sensors are wired in series, however, if the sensors are connected in parallel the sensors can be opened and the alarm system will not stop working. By connecting the stationary sensors in series, you will prevent people from disconnecting these sensors without the alarm going off.