who was the inventor of the light bulb and when was it developed
After many experiments, first with carbon filaments and then with platinum and other metals, Edison returned to a carbon filament. The first successful test was on October 22, 1879; it lasted 13.5 hours. Edison continued to improve this design and on November 4, 1879, filed for U.S. patent 223,898 (granted on January 27, 1880) for an electric lamp using "a carbon filament or strip coiled and connected to platina contact wires". This was the first commercially practical incandescent light.