So I had an argument with a friend, more like a discussion where we disagreed. It led to some interesting questions, or at least they are to me. I made a simple electromagnet using a battery, a nail, and an insulated copper wire wrapped around the nail many times with the ends of the copper wire being bare and connected to the battery terminals. Now we finally agreed that this was a short circuit...but what the hell does that really mean? So what if you connect the two terminals on a battery? Now he said the heat that I felt on my fingers, since my fingers were holding the bare ends of the wire to the terminals (I had a glove on), were simply because heat was produced from the short circuit. I told him the heat was definitely due to resistance. What's the truth? Are we both right? So to sum it up, what was the true cause of the heat and what on earth does a short circuit mean? Similar question about the short circuit, why is it that when you put a (+) and (-) end of a live wire (used to do this all the time with a battery charger), that it sparks or just goes berserk? Thanks guys.