Give scientific reasons.

In an electric bell, the electric current stops again and again.

On pressing the switch the circuit gets completed and the electric current flows through the coil which makes core an electro-magnet. It attracts the flexible iron strip which hits the gong and produces sound. But in this position the contact of the strip with the screw breaks and the current stops flowing. So flexible strip moves back and makes contact with the screw. This causes the current to flow again and iron strip again hits the gong.

Thus, due to this make and break arrangement the current stops again and again.