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30 RICHARDSON'S BLUEBOOK OF PROJECTION r
22. What is meant by a "mil-foot" as applies to resistance ? 7
23. Knowing the temperature coefficient, how may the resistance of a wire be calculated at any temperature?
Loss Through Resistance, page 37
24. Does power used in overcoming resistance represent loss?
25. Is high resistance in an electric circuit ever necessary?
26. What is one important function of the projectionist?
27. What should the projectionist do immediately upon taking charge of a projection room? c
28. Up to what point does the resistance of conductors change but little ?
Rheostatic Resistance, page 38
i
29. What function does the rheostat perform?
30. What becomes of the power (voltage) broken down (con
sumed) by rheostats?
31. Why must the supply pressure (voltage) be higher than the
arc voltage?
32. How is arc stability secured?
33. Is waste of power necessary to secure stability of the arc?
34. How can waste power sometimes be saved?
35. What may be qualified roughly as waste?
V kk^ 1
Resistance Elements, page 40 f
36. What should be the maximum resistance element tempera
ture ? ^ ^o-<
37. What constitutes the two resistance elements chiefly em
ployed ?
38. How are resistance elements mounted and insulated ?
39. What controls the amount of resistance offered?
40. What allowances must be made as to new wire coil or cold
grid resistance. 4Mvd
Coil and Grid Rheostats, page 41
* 41. Name the relative advantages and disadvantages of coil and grid rheostats.