Electric Bell

Construction

           The electric bell consists of an electromagnet. In front of the electromagnetic poles, there is a soft iron piece. The soft iron piece is attached to the vibrator. Vibrator is a rigid metallic strip having a hammer at its free end. The gong is fixed against the hammer. Also, platinum strip is fixed to the vibrator. By adjusting screw in contact-maker, contact is made with a platinum strip at a point. This point is called contact point. 

Working

               When key is pressed, the electric circuit is completed and the current flows through the electromagnet The electromagnet becomes magnetized and attracts the soft iron piece. When the soft iron piece is attracted, the hammer strikes the gong. The gong produces the sound. This movements breaks the circuit at the contact point between the screw and platinum strip, so that the current stops flowing. The electromagnet gets demagnetized and thereby the soft iron piece is released. The soft iron piece falls back to the original position and makes contact with the screw. The electric circuit is completed again. The above process keeps on repeating. Therefore the soft iron piece keeps on vibrating and giving rise to the continuous ringing of the bell. Electric bells are used as door bells and buzzers.