This course covers the theory of transformers by simulating them. The simulation models are built from first principles using fundamental laws of physics. To ease the process of bridging the gap between theory and simulation, we will begin with simple inductors and compare simulation results with theory. The course contain several code along sessions with all simulation models built using Python and with the free and open source circuit simulator Python Power Electronics. The final session contains a case study of a flyback converter where besides the theory of operation of the converter, the simulation also covers the high frequency transformer used.