Group III 



iPmit one question from this group.) 



7. Describe an experimental method of determining the coefficient of expansion 

 of a gas under constant pressure. 



8 A Centigrade mercury thermometer contains in its bulb and capillary tube 

 up to the 0° mark . 15 cubic centimeter of mercury. If the diameter of 

 the capillary tube is 0.012 centimeter, what is the length of the tube from 

 the 0° mark to the 100° mark ? (The coefficient of apparent expansion of 

 mercury in glass is 0.00015G.) 



9. How many kilograms of coal would be needed in a boiler having an efficiency 

 of 65 per cent to convert 50 kilograms of water at 10° C. into steam at 

 100° C. ? Assume that the heat value of the coal is 7,000 calories per 

 gram. 



Group IV 

 (Omit one question from this group.) 



10. (a) Explain in terms of the wave theory of light the production of a spectrum 



by means of a prism. 

 (b) Describe the appearance of the solar spectrum. 



11. (a) Describe an experimental method of determining the index of refraction 



of glass. 

 (6) The index of refraction of glass being 1.5, find the speed of light in it. 



12. The works of a watch are held 1 . 5 inches from a jeweler's eye-lens which has 



a focal length of 1 . 75 inches. How many times are the works magnified ? 



Group V 

 (Omit one question from this group.) 



13. Using diagrams describe an electric telephone transmitter and an electric 



telephone receiver and explain the action of each. 



14. A total current of 24 amperes flows through two branches of a divided circuit 



having resistances of 7 and 5 ohms, respectively. Find 



(a) The strength of current which flows through each branch. 



(b) The electromotive force required to maintain the current. 



15. An electric motor having an efficiency of 85 per cent develops 8 horse-power 



when connected to a 220-volt circuit. How much current flows through 

 the motor ? (One horse power = 746 watts.) 



