REVIEW. 439 



31. (a.) Discuss carefully the resistance of a Galvanic cell. (6.) 

 Describe the Voltaic arc. 



32. (a.) State the difference between a magnet and an electro- 

 magnet. (&.) Give the principles on which the telegraph operates. 

 (c.) What is meant by an "electronegative substance?" 



33. (a.) Describe Ruhinkorff's coil, and (6.) explain its action. 



34. Describe the thermo-electric pile, and explain its use. 



35. (a.} Give Prof. Tyndall's illustration of the propagation of 

 sound. (6.) What is the velocity of sound in air ? (c.) How is it 

 affected by temperature ? 



36. (a.) Explain the difference between noise and music. (&.) 

 Name the three elements of a musical sound, and state the physical 

 cause of each. 



37. (a.) Describe and explain the telephone. (6.) The phono- 

 graph. 



38. (a.) Explain interference of sound. (6.) Give the laws of 

 vibration of musical strings, (c.) Give the relative numbers of 

 vibration for the tones of the major diatonic scale. 



39. (a.) If 18 seconds intervene between the flash and report of a 

 gun, what is its distance, temperature being 82 F. ? (6.) If a 

 musical sound be due to 144 vibrations per second, how many 

 vibrations correspond to its 3d, 5th, and octave ? 



40. The bottom of a tank is 100 centimeters on one side, and a 

 meter on the adjoining side. The tank has a depth of 50 centi- 

 meters of water, (a.) What is the pressure on the bottom ? (6.) 

 On either one of the vertical sides ? 



41. (.) What is a horse-power? (&.) How many horse-powers 

 are there in a machine that will raise 8250 Ibs. 176 ft. in 4 minutes ? 

 (c.) State the modes of diminishing friction. 



42. What will be the kinetic energy of a 25-pound ball that has 

 fallen a mile ? (Reject small remainders.) 



43. Two bodies are attracting a third with forces as 441 to 576, 

 the first, weighing 25 Ibs., at a distance from the third of 20 feet, 

 and the second at a distance of 30 feet ; what is the weight of the 

 second ? 



44. How far will a body fall in the first second on Saturn, the 

 density of Saturn being .12 that of the earth, and its diameter being 

 72000 miles ? 



45. (a.) What is temperature ? (&.) Discuss the expansion of 

 water by heat, (c.) What is the rate of gaseous expansion by heat ? 



46. (a.) What is the difference between evaporation and boiling ? 

 (&.) What is the boiling point ? (c.) What is distillation, and how 

 is it performed ? 



