Sources of energy Worksheet-8

Sources of energy Worksheet-8

 

  1. What is gasohol? Where is it used?

 

  1. How is fission caused in U-235?

 

  1. State Einstein's mass-energy relation, Give the meaning of each symbol which occurs in it.

 

  1. Name two gases, other than carbon-dioxide that are given out during burning of fossil fuels and contribute towards acid rain formation.

 

  1. Out of two solar cookers, one was covered by a plane glass slab and the other was left open. Which of the two solar cookers will be more efficient and why?

 

  1. Why are many thermal power plants set up near coal or oil fields?

 

  1. Justify in one sentence that hydropower is a renewable source of energy.

 

  1. A student constructed a box type solar cooker. He found that it did not work efficiently. What could be the reason? Give any four possible mistakes in the construction and operation of the cooker. What maximum temperature can ordinarily be reached inside a solar cooker?

 

  1. A student has set up a solar cooker in a box by using a black painted aluminium sheet, a black cooking vessel, some glass wool, a glass sheet and a mirror plate. What is the role of each item used in the solar cooker?

 

  1. Solar energy can be harnessed directly as well as indirectly. Give two examples of each type.

 

Answer:

  1. Gasohol is mixture of petrol (gasoline) and alcohol. It is used as a fuel in specially converted car engines.

 

  1. Fission m U-235 is caused by hitting U-235 target with slow neutrons.

 

  1. Einstein's mass-energy relation is E = mc2, where m = mass that disappears, E = energy that appears and c = velocity of light in vacuum = 3 × 108 m/s. When m is in kg, E is in joule.

 

  1. Sulphur dioxide and Nitric oxide.

 

  1. The solar cooker covered by plane glass slab will be more efficient than the other one. Because the plane glass slab enables the cooker to trap heat inside it. So the temperature inside the cooker rises. In fact, the plane glass slab placed on the cooker produces a kind of greenhouse effect.

 

  1. Coal or petroleum is used to heat water to generate steam required for running the turbines in thermal power plants. Thus, if thermal power plants are set up near coal or oil fields, the cost of transportation of coal or petroleum is greatly reduced.

 

  1. Hydropower is generated from water flowing out of the dam which gets filled up again when it rains through the rivers which supply water to the dam.

 

  1. The four possible mistakes in the construction and operation of the cooker are :

(i) the interior of solar cooker might not have been blackened or properly blackened,

(ii) plastic cover might have been used instead of glass cover,

(iii) the cooker might not have been properly insulated,

(iv) The cooking utensils might not have been blackened.

 

  1. (i) Black painted aluminium sheet absorbs heat radiation.

(ii) Glass wool is a bad conductor of heat, so it prevents the loss of heat.

(iii) Glass sheet traps the heat radiation in the box.

(iv) Mirror plate reflects the heat radiation onto the glass sheet.

 

  1. Solar energy is used directly as heat or by converting it directly into electricity.

Examples : Solar cooker (or solar water heater) and solar cell panels.

Solar energy is used indirectly by converting it into chemical energy (like biomass energy), harnessing the energy of wind, sea waves, tides and ocean thermal energy.

Examples : Biogas plants and windmills.