Georg Ohm is not known for any major inventions. He did, however, discover Ohm's law, which indicates the directly proportional relationship between the current flow through a conductor and the voltage as well as the inversely proportional relationship between the current flow and the resistance.
Ohm's work led to a number of theoretical and practical advancements with respect to current electricity. The slide wire potentiometer, a type of variable resistor, is one of the inventions that resulted from Ohm's work. The unit of electrical resistance, the ohm, is named after him. His work was not initially well received, but Ohm's peers eventually recognized its importance, and he received a number of honors during his lifetime.