I had just finished my first semester of circuits class, where we of course covered the idea of equivalents. We had also just touched on voltage dependant current sources and current dependant voltage sources. Since we had never combined the two ideas, I figured I could try putting one on the equivalent circuit. Maybe an active device would react differently than the passive RLC components we talked about in class? It turns out that if you put a voltage controlled current source on the terminals, and then proceed work through some math you can prove the difference as long as you ignore a minus sign on the first step. I figured I had also better also try out a current controlled voltage source, which I was actually did correctly. As I was redoing the math for the first case, the interviewer finally took pity on me an explained about the heat/power cord technique.
I felt really bad, until I went back to my dorm and asked many of peers who were all as stumped as I had been.