a. Explain what is meant by an ohmic conductor.

b i. Sketch a graph of resistance R against voltage V for a wire of pure iron kept at constant temperature. Label this line X.

ii. Sketch a graph of resistance R against voltage V for a second wire of impure iron, of the same diameter and the same length, which is kept at the same temperature. Label this line Y.

iii. Explain how the graphs would change if the wires were kept at a higher, but still constant, temperature.

c. Deduce how the resistance of a wire made of pure iron would change if both the diameter and the length were doubled.