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Group III 

 {Omii one question from this group.) 



7. A steel tape 100 feet long and correct at G0° F. is used for measuring a base 



line on a day when the temperature is 85° F. The observed length is 330 

 feet. If the coefficient of linear expansion of the tape is 0.0000058 per 

 degree Fahrenheit, what is the true length of the base line ? 



8. (a) Distinguish between temperature and quantity of heat. 



(b) State some evidence in verification of the statement that heat is a form 



of energy. 



(c) Explain what is meant by the mechanical equivalent of heat. 



9. Two hundred grams of snow at 0° C. are contained in a cup the thermal 



capacity of which equals that of 12 grams of water. Steam at a tempera- 

 ture of 100° C. is turned into the snow, melting it and raising the tempera- 

 ture of the resulting water to 40° C. Assuming no loss or gain of heat, 

 find how much steam is used. 



Group IV 

 {Omit one question from this group.) 



10. (a) Explain carefully all that will happen to a ray of sunlight when passed 



through a triangular glass prism. 

 (b) Why does a green leaf appear nearly black when seen in a red light ? 



11. (a) Describe the construction and use of some form of photometer. 



(b) A 16-candle-power lamp and a standard candle are placed 5 feet apart. 

 At what position between them should a screen be placed that its two 

 sides may be equally illuminated ? 



12. (a) A camera has a lens whose focal length is 15 centimeters. How far from 



the lens is the photographic plate when there is focused on it the image 

 of an object 300 centimeters away from the lens ? 

 (b) If the image is 10 centimeters in height, what is the height of the object ? 



Group V 

 {Omit one question from this group.) 



13. (a) A bar magnet is broken into three pieces of equal length. Describe the 



magnetic condition of these pieces. Illustrate by diagram. 

 (6) Describe a method for determining the sign of the electrification on a 

 charged body. 



14. A small arc lamp requires a current of 5 amperes and a difference of potential 



between its terminals of 45 volts. What resistance must be connected in 

 series with it in order to use it on a 110- volt circuit? 



15. A current of electricity passed through a coil of wire hax'ing a resistance of 



10 ohms heated 1000 grams of water from 15° C. to 61 .08° C. in 5 minutes. 

 What was the strength of the current? 



