GENERAL KNOWLEDGE

Detailed explanation-1: -When Bell spoke into the open end of the drumlike device, his voice made the paper and needle vibrate. The vibrations were then converted into an electric current which traveled along the wire to the receiver.

Detailed explanation-2: -He also worked in medical research and invented techniques for teaching speech to the deaf. Bell’s extensive range of genius included patents for the telephone and telegraph, the photophone, aerial vehicles, and hydro-planes.