Doonesbury by Garry Trudeau for May 10, 2006
Voice: So we just think Cornell would be a great fit for you, Alex! Alex: Let me ask you a question, Professor... two black boxes, each hiding an internal circuit. Using workbench tools, how do you tell which is the current source and which is voltage? Voice: Well, Alex, they're Thievenin and Norton equivalences, so tools are useless. You'd have to hold the boxes in your hand. Since the curent source has a resistor, it'd be warmer. Fun question - why do you ask? Alex: I'm so going to Cornell!