1.  For every 100 J of solar energy shining on a photocell, only 5 J is transferred to useful

         energy (as electricity).

         a) What happens to the other 95 J?

         b) What is the efficiency of the photocell?

    2.  In a power station, for every 100 J of chemical energy stored in coal, 10 J is wasted in the boiler,

         30 J is wasted in the cooling tower and 8 J is wasted in the generator. The rest of the energy is

         converted to electricity.

         a) Calculate the amount of energy that is converted to electricity.

         b) Calculate the efficiency of the power station.