The force responsible for the movement of the hammer in the circuit, when it is completed and the hammer strikes the gong, is the magnetic force. This happens because when the electric current flows through the coil in the circuit, it creates a magnetic field, turning the coil into an electromagnet. This magnetic force attracts the soft iron armature connected to the hammer, causing the hammer to move and strike the gong

. Thus, the movement of the hammer is due to the magnetic force generated by the current flowing through the coil.