Main Question or Discussion Point
A twisted cylindrial rod has the cross sectional symmetry so that it's not posible to tell whether it is twisted or not without knowing if there is any torsional energy. now drawing a line on the surface of it can tell us whether or not it's twisted. It might not be a straight line.. there are infintes of such lines and any one of them would tell us the difference. could anyone explain what difference would it make if i draw a line on a untwisted surface and twisted one... though i got the idea mostly but having problem in visualization.