DC in transformer

One of my greatest sources of inspirational gurus has been Prof. M. V. Hariharan of IIT Bombay. What truly set him apart was his remarkable ability to explain complex concepts in the simplest possible way.
On one occasion, I asked him what I thought was an innocuous question: “Can DC pass through a transformer?”—expecting a straightforward and emphatic “No.” Instead, he took the time to respond with handwritten notes (typing—especially equations—was never his preferred medium!). The explanation was illuminating and left a lasting impression on me. I got it typed then. 

Recently, while cleaning up my hard disk, I rediscovered that file—fortunately not deleted over the years. I’m sharing it here so that you, too, can experience the same joy and clarity I felt when I first encountered such a beautifully simple explanation of a difficult topic.  click here to open file