If the temperature of a metal is raised, the amplitude of the vibrations of the metal-lattice ions increases.

(a) What effect, if any, do you expect these greater vibrations to have on the resistance of a piece of that metal?

(b) What effect does running a current in a metal have on the temperature of the metal?

(c) Make a graph of current versus potential difference, taking into account the effect you described in part \(b\).