So I’m fairly upset with myself for not working on my latest Circuits assignment a lot earlier…
I turned it in at the end of class today, but I’m not hoping for much. Why not, you ask? Well, let’s just say I had to start fudging calculations when I found an input resistance of -5002.14 ohms. (I arbitrarily dropped the negative…)
Non-nerdy explanation of why that’s bad: Short answer: It’s impossible.
Long answer: You can imagine the circuit I was looking at like a water pipe with a filter/funnel in it. The filter is designed so that for just a small amount of water going through, it’s not too hard and the water pretty much goes right through. But, the more water you try to send down the pipe, the more “clogged” the filter gets, and the harder each molecule of water has to work to get past the filter. How “hard” a molecule has to “work” is like the resistance number I calculated for my circuit: Maybe the filter is designed so that each molecule needs 500 Joules of energy to get past the filter, per gallon of water that flows through. So, if 1 gallon flows, each molecule needs 500 Joules. If 2 gallons flow, each needs 1000 Joules, and so on. The more water flowing, the more energy needed. This is basically how resistors in electronic circuits work.
Now imagine what it would mean if that number was negative… i.e., you get energy back by pushing your way through a filter. And you get more back the more water there is. It doesn’t make any sense, which is why I know my homework is wrong. 🙁
To quote Wikipedia, “Absolute negative resistances without an external energy source cannot exist as they would violate the law of conservation of energy.”