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• 2,500,000 kg of water passes through a hydroelectric generator. The change in gravitational potential energy of the water is 367.5 MJ.

  gravitational field strength = 9.8 N/kg

  Calculate the mean change in vertical height of the water as it moves through the hydroelectric generator.

  367.5 MJ = 367,500,000J

  367,500,000 = 2,500,000 x 9.8 x h

  h = 367,500,000 / (2,500,000 x 9.8)

  h = 15m
• The generator transfers 3.0 kW of electrical power. Calculate the time taken for the generator to transfer 2.16 × 107J of energy. (in standard form)

  3 kW = 3000 W

  3000 = 2.16 x 10^7 / t

  t = 2.16 × 10^7 / 3000

  t = 7200s

  t = 7.2 × 10^3s
• A solar power system is installed in the remote village in addition to the hydroelectric generator. Explain why this improves the reliability of the electricity supply to the village.

  In the summer the power output from the hydroelectric generator will be lower but the solar power output will be greater.

  This means there is little variation in the total power output.