XII.J PROBLEMS. 349 



38. Make a study of devices for indicating synchronism and 

 of methods for synchronizing. 



39. Construct a shunt for an A.C. Wattmeter so as to extend its 

 range ; it should be designed so as to be correct at different fre- 

 quencies. 



40. Determine the losses of a machine by the retardation method; 

 see Standard Handbook. 



41. Determine the hysteresis loss in different dielectrics. 



42. Set up and test an electrolytic or a mercury arc rectifier. 



43. Make a study of potentiometer methods for measuring alter- 

 nating currents and voltages. 



44. Make a comparison of the behavior of various types of 

 instruments at commercial frequencies and at high frequencies. 



45. Determine the current efficiency and energy efficiency of a 

 storage cell. 



46. Adapt the Ryan-Braun Tube to the measurement of power 

 particularly of small power. 



47. With an oscillograph, study the behavior of fuses and circuit 

 breakers with D.C. and A.C. loads, inductive and non-inductive. 



48. Determine the instantaneous values of resistance, for example, 

 of a lamp with alternating current, or with direct current at brief 

 intervals of time after the circuit is closed. 



49. Determine the instantaneous values of flux in a transformer, 

 either indirectly (from instantaneous values of current and voltage) 

 or directly by some special device; see Bulletin of the Bureau of 

 Standards, Vol. IV., p. 467. 



50. Make a study of different methods and apparatus for measur- 

 ing one of the following quantities, with a view to determining their 

 relative advantages and developing modifications of new methods: 

 (a) slip; (6) frequency; (c) speed; (c?) phase; (c) form factor; (/) 

 wave form; (g) power factor; (h) reactive factor; (i) very small 

 (or large) alternating current, voltage or power. 



51. Make a study of an interpole motor, repulsion motor, series 

 A.C. motor, or other particular machine. 



52. Make a study of " concatenation," or other method of speed 

 control for induction motors. 



53. Determine the wave form of alternating electromotive forces 

 and currents by means of the Pierce Analyzer ( na, Exp. n-A) and 

 by other methods. 



