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                  Question 1  
                           
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                  (1)       (a)       (i)         Sketch the thermo-syphon cooling  system. 
                                    (ii)        Label four parts of the sketch in 1 (a)(i). 
                                    (iii)       State two demerits of the thermo-syphon cooling system 
                       (b)       Explain the term convection current. 
                      
                      
                      
                      
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                    The candidates, who attempted this  question, responded well to parts (ai) and (aii).  However parts (aiii) and (b) were difficult  for them.  The required responses to  these parts are given below: 
                    (aiii)     -           it requires large water passages to  ensure unrestricted flow; 
              -           it requires high radiator height or  bulky radiator; 
              -           it requires a big bonnet; 
              -           it requires large quantity of water; 
              -           water circulation is slow. 
                    (b)       This refers to the circulation of water  due to change in densities i.e. the hotter water moves to the top while the  colder moves down. 
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