Alfonso Bachiller Soler is a full professor in the Department of Electrical Engineering of the University of Seville, where he teaches courses related to electrotechnics and circuit theory, among others. He received both the Industrial and Aeronautical Engineering degrees, and the Ph.D. degree, from the University of Seville, Spain.Ramón Cano González is a full professor in the Department of Electrical Engineering of the University of Seville, where he teaches courses related to electrotechnics and circuit theory, among others. He received the Industrial Technical Engineering degree, the Automation and Industrial Electronic Engineering degree, and the Ph.D. degree, from the University of Seville, Spain.Miguel Ángel González Cagigal is an assistant professor in the Department of Electrical Engineering of the University of Seville, where he teaches courses related to electrotechnics and circuit theory, among others. He received the Industrial Engineering degree, the M.Sc. in Industrial Engineering, the M.Sc. in Electric Energy Systems, and the Ph.D. degree from the University of Seville, Spain.

• 1. Theorems.- 2. Solved problems .

Alfonso Bachiller Soler is a full professor in the Department of Electrical Engineering of the University of Seville, where he teaches courses related to electrotechnics and circuit theory, among others. He received both the Industrial and Aeronautical Engineering degrees, and the Ph.D. degree, from the University of Seville, Spain.Ramón Cano González is a full professor in the Department of Electrical Engineering of the University of Seville, where he teaches courses related to electrotechnics and circuit theory, among others. He received the Industrial Technical Engineering degree, the Automation and Industrial Electronic Engineering degree, and the Ph.D. degree, from the University of Seville, Spain.Miguel Ángel González Cagigal is an assistant professor in the Department of Electrical Engineering of the University of Seville, where he teaches courses related to electrotechnics and circuit theory, among others. He received the Industrial Engineering degree, the M.Sc. in Industrial Engineering, the M.Sc. in Electric Energy Systems, and the Ph.D. degree from the University of Seville, Spain.

• 1. Theorems.- 2. Solved problems .