When the circuit breaker is at ‘ON’ position, current is below the limit and magnetic field produced by the solenoid is too weak to attract the iron lever. Springy metal are still in contact with the contact and the circuit is completed. Current flows normally through the circuit.
When there is a sudden surge of current (electric fault like short circuit), the magnetic field produced by the solenoid now is very strong. Iron lever will be attracted to it and spring will be able to pull the springy metal out such that the springy metal is no longer in contact with the contact and the circuit is open. The electromagnet then loses its magnetism and no longer attract the iron lever, which in turn falls back.
After the electric fault is repaired, the user can reset the circuit breaker by pushing in the reset button, which pushes the springy metal to be in contact with the contact again and close the circuit.
When the bell button is pushed down, the circuit is closed and current starts to flow. The electromagnet becomes magnetized and attracts the iron armature towards it, which causes the hammer to hit the gong.
At the moment the hammer moves towards the gong, the circuit is open as armature is no longer in contact with the contact. The electromagnet then loses its magnetism such that the springy metal is able to pull back the iron armature to be in contact with the contact and closes the circuit again. The cycle repeats when the user presses the button again.
