A perfect varistor is a constant voltage resistor as function of current through the resistor. can't exist, because its resistance would be infinite at zero current. In electronic devices, varistors are often used surge protectors. can in place an ordinary discharge across superconducting coil sections. When this way, integral I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="h...