The diagram below shows the variation of electrical resistivity with temperature for three different metals.
(a) Explain why metals are good conductors of electricity.
(b) Explain the difference between 'resistance' and 'resistivity'.
(c) Explain why the resistivity of a metal increases with temperature.
(d) Use the graph to calculate the resistance of an iron wire of length 2.0 m and radius 0.50 mm at a temperature of 100 °C.