Define solar constant.

105 A student constructed a box type solar cooker. He found that it is not working efficiently. What could this be due to? Give any four possible mistakes that he could have made? 106 What are the advantages of using solar water heater? Draw a labeled schematic diagram for a solar water heater. 108 What is the main basic cause for winds to blow? Compare wind power and power of water flow in respect of generating mechanical and electrical energies. 109 Write two limitations of wind mill.