7- What determines the magnitude of (a) i° C. ? (b) i° F. ? In what respects 

 would a gas thermometer be (a) superior and (b) disadvantageous as com- 

 pared with a mercury, or Hquid thermometer ? Explain. 



8. How many grams of steam will be produced if i,ooo gm. of lead of specific 



heat 0.032 at a temperature of 300° C. are dropped into 100 gm. of water 

 at 80° C. contained in a calorimeter of specific heat o. i and weight 90 gm. ? 



9. Why does hot air rise ? Why does frost appear on the inside of a window 



pane in one's living-room before it appears on the outside of the pane? 

 Why are hot-air registers placed near the ceiling and cold-air registers 

 placed near the floor in mechanically ventilated schoolrooms ? What is 

 the cause of the loud hammering heard in certain steam radiators in the 

 early morning and how may the trouble be remedied ? Why are fur- 

 nace pipes placed near the inner walls of a room heated by hot air and why 

 are steam radiators placed near the outside walls of a room heated by 

 steam ? 



10. Describe a laboratory experiment that you performed in which you used 



some form of mirror, either plane or curved. Do this very completely, 

 drawing diagrams whenever possible. State not only what you did but 

 also what you found to be true as the results of your experiment. 



1 1 . A camera with a lens whose principal focal distance is 4 in. permits the lens 



to be drawn out to a maximum distance of 5 in. from the plate. 



a) What is the shortest distance from the lens at which a flat object may be 



placed in order to secure a properly focussed image ? 



b) If the object is 8 in. high, what will be the height of its image ? 



12. Why does one's face appear so ghastly and one's hps so purple when seen by 



the light of a mercury- vapor arc lamp ? Would the addition of a colored 

 shade to the lamp improve the situation ? Explain. 



13. Describe an experiment that you performed in the laboratory in which a 



voltmeter or ammeter or some form of galvanometer was one of the pieces 

 of apparatus used. Draw diagrams where helpful, and state, not only what 

 you did, but also the object of the experiment. 



14. a) A battery, whose e.m.f. when delivering no current is 2 volts and whose 



internal resistance is 6 ohms, sends a current of j ampere through an 

 external resistance connected across its terminals. Find the value of 

 the external resistance. 

 b) How many watts are supplied to the external resistance ? 



15. a) Explain clearly what is meant by an alternating current. 



b) What are the advantages and disadvantages of an alternating current 

 as compared with a direct current ? 



