While looking at reviews for Caver A. Mead's book, I read a review that said he made a mistake including voltage in a calculation for superconductors.
Now I think that there must be voltage of a type in superconductors, there are 2 types of voltage. One is the voltage drop across a conductor. This is similar to the voltage on a charged capacitor. But there are other type is kinetic voltage, this is where a charge is moving at a given velocity as it used in particle accelerators. Voltage of this type can be compared to (or come from) inertia, and if electrons are moving then there will be some persistence even if impedance is removed since electrons still have mass. If a superconducting ring that carried a current was suddenly opened, the electrons are still moving and must compress slightly as they come to a stop leaving the ends momentarily charged to some degree. Additionally imagine a superconductive loop in an alternating EM field, there is a voltage induced by the changing magnetic field (or relativistically distorted electric field) and this does not lead to a voltage drop, but there is still a voltage, if this loop was opened and a normal circuit inserted you would indeed see a voltage. Indeed even if we use a resistive wire in such a loop, no voltage drop is noted, and yet there is still a voltage present to overcome the resistance, and the resistance is still impeding the flow of electrons. But would it be correct to say that this is happening with no voltage, even though none can be read by any instrument? John
