1. The problem statement, all variables and given/known data In all physics textbooks, the V-I graph for diode appears like the followings http://220.127.116.11/phpBB2/forum_img/diode/diode-14.gif However, when I conducted the experiment with a 1N4001 diode and 12V-AC, similar graph was found, the the graph seemed to have reflected along the y-axis. 2. Relevant equations 3. The attempt at a solution sorry people, but I have no idea why it is this way. Since the x-axis should represent the voltage supplied. What I'm thinking is that the x-axis is in the opposite direction on a C.R.O., which means more positive towards the left and more negative towards the right. Is that how a CRO works?