The reed switch is placed between the poles of the strong permanent magnet. State and explain what happens.

he switch is open when the magnetic field is activated, a magnetic force is applied to the reed, which causes it to move, closing the circuit and allowing the lock to open.

Explanation:

The reed switches, this is metallic, generally iron, in general the switch is open when the magnetic field is activated, a magnetic force is applied to the reed, which causes it to move, closing the circuit and allowing the lock to open.

The force is given by

                 F = i l x B

In the systems when the switch is depressed the magnetic field is created in a solenoid and this field attracts the metal of the reed.