General Thought Questions 241 



27. When the insulation wears off a lamp cord, why does a fuse often 

 blow out? 



28. Why are thick steel rods used as lightning rods rather than thin 

 wire? 



29. Would a heavy car or a light car, having the same braking surface, 

 be likely to wear out its brakes first? Why? 



30. Why do fogs often fill hollows and not the high points? 



31. If wind sets in from the northeast, from what direction will an 

 approaching storm arrive? 



32. Discuss in a paragraph a drinking water supply under the following 

 heads: (a) its source and the reasons for the selection of this source, 

 (b) how the water pressure is secured and how the water is brought 

 to a town or city, (c) sanitary precautions for keeping the water pure. 



33. Why do some outfielders in baseball start running when they hear the 

 bat strike the ball though they do not yet know just where they are 

 to go? 



34. Will a white post or a black post cast a darker shadow? 



35. A part of the current that comes to a trolley car from the wires 

 passes through the rails. Why do we not get a shock if we touch 

 the rails? 



36. What property of hydrogen makes it good for use in airships and 

 what property makes it dangerous? 



37. Why does a toy motor 1 make more noise when running on the bare 

 floor than when running on carpet? 



38. Why is it advisable to have lightning rods grounded in moist earth 

 rather than in dry earth? 



39. Name some advantages of electric power over steam power for run- 

 ning (a) factories, (b) street car lines. 



40. Why do rubber suction discs stick to a wall? 



41. Why will hot liquid cool quicker in a tin cup than in a wooden 

 bowl? 



42. Is it true or false that rainwater drawn from the ocean by the sun is 

 different from 1 rainwater drawn from a lake? 



43. Why is it hotter on a white sandy beach than on dark earth? 



44. Why does a dentist use a concave mirror in his work? 



45. Why is it advisable not to fill an automobile radiator to the top 

 with an anti-freezing mixture? 



46. Why does a lake change color under different weather conditions? 



47. Is food chilled more quickly if placed at the top than if placed 

 at the bottom of a refrigerator? 



48. How does an electric fan cool us? 



49. Suggest ways in which the free-moving property of air is an aid to us. 



