Made by Faraday in his laboratory in the basement of the Royal Institution in August 1831, thus creating the first ever electric transformer.
During the 1820s Faraday sought to discover how to make electricity from magnetism. He achieved success with the device pictured above on 29 August 1831. It's made from everyday materials such as wire made for bonnets, although the iron ring seems to have been specially made.
Making the induction ring was a tedious process since Faraday had to wind the coils of wire on opposite sides of the ring and insulate them with cotton. He doesn't mention the time taken in his diary but it was probably about ten working days.
When he passed an electric current through one coil he induced an electric current in the other coil, which flowed for a very brief period of time.
This object is currently on display in the Lower Ground Floor of the Royal Institution in the Faraday Museum.