These two circuits will function as a broken loop warning device. Can think of this as a circuit that sets off an alarm when a loop of wire is cut. This cut wire could also represent a sensor that is normally closed and then goes open circuit when some parameter is exceeded. This kind of sensor is normally used because it automatically sets off the alarm if the wires to the sensor get damaged.
There are two circuits shown in the figure that can do this, one based on a BJT and one based on a MOSFET. They both have the same kind of operating principle.
The function of the circuit is to react and let current flow through the alarm when the wire loop is broken. The breaking of the loop is a switching event and the reaction of the transistors is also needs to be a switching event. Therefore, The transistors are modelled as switches that turn on and off.
If these two circuits were to operate under identical conditions and needed to be battery powered, Which transistor circuit would be better to use over the other for the longest battery life.
I would choose a MOSFET as a MOSFET is a lot faster than BJT and therefore, it will switch a lot faster than BJT. Also, aren't MOSFETS more efficient and BJTs consume more power?
Please let me know if I have said anything incorrect or if I could add anything, thaks!