This extensive quantity can be toggled between high and low values by using a spin valve. This quantity depends strongly on magnetic field strength in a phenomenon whose study earned Albert Fert and Peter Grünberg the 2007 Nobel Prize in Physics, in whose name this quantity's name is preceded by "giant magneto-." A device primarily used to directly change this quantity results from using only two of three terminals of a potentiometer. (10[1])This quantity can be directly (-5[1])changed by using a rheostat, (10[1])which (10[1])on circuit diagrams (10[1])is represented by (10[1])an arrow (10[1])pointing through a rectangle. (10[1])This quantity provides the real contribution to impedance. After cooling below the the critical temperature, this extensive quantity drops to zero in superconductors. (10[1])For 10 points, name this quantity measured in ohms which quantifies (10[1])opposition to current flow. ■END■