/kloc-before the advent of electric light in the 0 th and 9 th centuries, kerosene lamps or gas lamps were widely used in daily life. This kind of lamp emits light by burning kerosene or gas, so it will emit strong black smoke and pungent smell, and it is very troublesome to use because it needs to add fuel and scrub the lampshade frequently. There is a more serious problem, that is, this kind of lamp can easily cause fires and disasters. At that time, many scientists were trying to develop a safe, reliable, convenient and durable electric lamp by using the alternating current that had appeared at that time.