Zero electrical resistance is also called superconductivity. The Meissner effect states that when superconducting materials reach their critical temperature two exciting properties appear. Firstly, the electrical resistance of the material drops rapidly to zero and secondly, they become perfect diamagnets (they exclude all magnetic flux from the superconductor). Superconducting magnets are used in accelerators. These machines rely on zero resistance in order to function properly. The magnets are cooled to extremely low temperatures, below the critical point of the material at which it becomes a superconductor.
