False Claim Response:
When a student uses a voltmeter to measure the electric potential at various positions on the surface of an irregularly-shaped charged hunk of metal, she will get readings that are the same all in locations. The surface is euipotential. A hunk of metal is a conductor. This means that charges are free to flow within and along its structure. If excees charge resides on a conductor, the charges will very quickly spread out as much as possible due to electrostatic repulsion of like charges. This means that all excess charge will reside on the surface of the conductor and a dynamic equilibrium will be established such that there will be no net motion of the charge along the surface. When this is the case, there can be no net electric force acting along the surface on the excess charge, otherwise net motion would occur. No net electric force along the surface implies no net electric field along the surface (F=qE). No electric field along the surface implies no change in electric potential along the surface (ΔV=∫E·dx). Thus the surface must be equipotential. All voltmeter measurements made on the surface, regardless of whether or not excess charge is on the sample, will have the same reading.