Simplify the following text for a Grade 10 native English-speaking person.
Original: Bardeen was a Professor of Electrical Engineering and Physics at the University of Illinois at Urbana-Champaign from 1951 to 1991 .
Simplified: He joined the engineering faculty and the physics faculty at the University of Illinois at Urbana-Champaign in 1951 . He was Professor of Electrical Engineering and of Physics at Illinois .