Answer one of the following two questions.

Value of this section: 10 marks

1. Derive a formula for the differential of G and use it to determine . [10 marks]
2. The coefficient of thermal expansion at constant pressure is defined by

   

   1. For copper, . By what fraction does a copper wire expand when its temperature increases by during normal operation over the course of a warm day? [2 marks]
   2. Show that

      

      where L, h and w are the length, width and height of a wire with a rectangular cross-section. Provide an argument showing that we may simplify this equation to

      

      [5 marks]

      Hint: No calculus is required here beyond a straightforward application of the product rule.

   3. A 120m length of copper wire spans the distance between two transmission towers. How much longer is it after warming by ? [3 marks]