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3 marksExpansion

CSEC Physics · 1995 · Paper 2 · Question 3(a)(i)

A family uses electricity for heating water used in their home. The 1.5 kW electric water-heater is controlled by a thermostat so that it is switched on for an average of four hours each day. A simplified diagram of the thermostat is shown in Figure 3.

Explain how the thermostat works.

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Other parts of this question

  1. 3(a)(ii)What would be the effect on the working of the thermostat if the bi-metallic strip were inserted with the iron uppermost?[2 marks]
  2. 3(b)(i)What is the cost per year of the operation of the water-heater if one kilowatt-hour costs 40 cents?[4 marks]
  3. 3(b)(ii)To save money, the family considers installing a solar water-heater costing…[2 marks]
  4. 3(c)One of the reasons for having a glass cover over the collector plate of the solar water-heater, shown in Figure 4, is to take advantage of the glass-house (or…[3 marks]

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