OK, here is my frustration: I go to my lab, exhange equipment several times because some equipment is bad or wrong, do an experiment to show the time constant. First we charge the capacitor. Trial and error to find a good time increment. THEN, its time to discharge. AFTER 10 minutes of the capacitor not discharging (or shall we say, after 10 minutes it only discharged 1/2 volt, then 20 minutes another 1/2 volt gone...) we ask the teacher what could be wrong. She gives us a lecture on how we should have done the calculations and pre guessed what should be happening. Well, its not happening even with experimentor bias... which wouldn't have made a bit of difference. :grumpy: Can ANYONE give me a clue as to why the capacitor didn't discharge correctly? It charges at about 63% and SHOULD discharge at 37%, but ours would have taken days, I'm afraid. She didn't have an answer, except to sit there for the rest of the day to see how long it takes.