1. The problem statement, all variables and given/known data This is actually a lab experiment which includes a stretched string which is clamped to one end with a G-clamp and the other end with a pulley and some masses hung from it. There's a bar magnet placed underneath the string near the pulley and a movable bridge to alter the length of the string. It's connected to an AC supply and a rheostat. 2. Relevant equations L= lambda / 2 but I don't know what lambda is. 3. The attempt at a solution I've connected everything together but I get no vibration at all. Pictures attached below. Any help at all will be seriously appreciated!