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Group HI 

 (Omit one question from this group) 



7. a) Describe, by the aid of a diagram, the construction of a reciprocating 



steam engine and explain its operation. 

 h) In what respects does the steam escaping from the cylinder of the 

 engine differ from that entering it ? 



8. Three pounds of water at a temperature of 50° F. are contained in an 



aluminium kettle (specific heat =0.22) weighing 2 pounds. If one cubic 

 foot of gas when burned suppHes 600 B.T.U. how many cubic feet of gas 

 are needed to turn one-haK the water in the kettle into steam, assuming 

 no loss of heat ? Consider the atmospheric pressure to be normal. The 

 latent heat of vaporization of water =972 B.T.U. per pound. 



9. One thousand grams of liquid ammonia at 0° C. enters the pipes of an ice- 



making machine and leaves them as gas at 0° C. How much water at 

 10° C. will it change to ice at 0° C. ? The heat of vaporization of ammonia 

 is 450 calories per gram. 



Group IV 

 ((Dmit one question from this group) 



10. Explain the meaning of the following terms used in connection with light: 



refraction, index of refraction, critical angle, reflection, dispersion. 



11. A tree 55 feet high stands on the edge of a pond. From the opposite bank a 



man whose eyes are 5 . 5 feet above the level of the pond, and who is stand- 

 ing 18 feet from the edge of the pond, sees the reflected image of the tree 

 with the top appearing to just touch the edge of the pond nearest to him. 

 How wide is the pond ? 



12. An image, 10 feet by 12 feet in size, of a lantern slide, 2.5 inches by 3 inches 



in size, is thrown upon a screen 40 feet from the lens of the lantern. 

 a) What is the focal length of the lens ? 



6) If a larger image were wanted, should a lens of greater or of less focal 

 length be used ? State reason for your answer. 



Group V 

 {Omit one question from this group) 



13. a) What are the essential parts of an alternating current generator? 

 h) Describe its operation. 



c) Does it create electrical energy ? Give reason for your answer. 



(THIS EXAMINATION IS CONTINUED ON PAGE 3) 



