Lakhmir Singh Physics Class 10 Solutions Page No:150
Question 42: A certain form of energy is available due to the difference in the temperature of water at the surface of the ocean and its deeper levels.
(a) Name the form of energy.
(b) Is this energy ultimately derived from the sun or not ?
(c) Explain how this form of energy can be converted into electricity.
(d) What is the minimum temperature difference in water at the surface of ocean and its deeper level which is required to operate power plants based on this energy ?
Solution : (a) Ocean thermal energy
(c) Ocean thermal energy is used to generate electricity in an Ocean Thermal Energy Conversion power plant (OTEC power plant). A temperature difference of 20oC or more between the surface water and deeper water is needed for the operation of these plants. The warm surface water of ocean is used to boil a liquid like ammonia or chlorofluorocarbon. The high pressure of liquid vapours is used to turn the turbine of a generator and produce electricity.
Question 43: (a) The gravitational pull of the moon causes the sea-water to rise periodically.
(b) What name is given to the condition of the sea when its water is raised ?
(c) What name is given to the condition of the sea when its raised water recedes ?
(d) What name is given to the energy which can be harnessed from this natural phenomenon ?
(e) Draw labelled diagram to show how this energy can be harnessed to generate electricity.
Solution : (a) High tide
(b) Low tide
(c) Tidal energy
Question 44: When the material A mined from the earth is heated strongly in an insufficeint supply of air, it produces a solid fuel B which consists mainly of carbon. When another material C obtained from trees is heated in an insufficient supply of air, it produces another solid fuel D which also consists mainly of carbon. Name A, B, C and D.
Solution : A is coal; B is coke; C is wood; D is charcoal
Question 45: A certain form of energy which is not sourced directly or indirectly from the sun and does not cause any pollution is very easily converted into electricity. This form of energy is, however, not available everywhere. Moreover, it is technically very difficult and expensive to obtain it. Name the form of energy.
Solution : Geothermal energy.