F. H. Richardson's bluebook of projection (1935)

Record Details:

Title:
F. H. Richardson's bluebook of projection
Date:
1935
Publisher:
New York : Quigley Publishing Company, Inc.
Volume:
F. H. Richardson's bluebook of projection
Leaf #:
00063
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
{"Media History Digital Library","Jeff Joseph"}
Coordinator:
Media History Digital Library
Description:
Date Added:
March 21, 2024
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RESISTANCE Use on A. C. Bad Practice 45 (54) It is poor practice to use rheostatie resistance to control an a. c. light source. The proper instrument is a transformer. The waste is far less, the general results better and a rheostat on a. c. is apt to be noisy because of the inductive effect previously mentioned. Adjustable Rheostats (55) Rheostats may be had with fixed resistance, or with resistance that may be adjusted, within certain fixed limits, from time to time. Adjustable resistance is diagrammatically illustrated in Fig. 12, showing two binding posts, with certain resistance elements so connected that all or only a part may be used. Figure 12 (56) A is one circuit wire and B the other. Wire B connects to the arc through lever 6 and contacts 1, 2, 3, 4 and 5 upon any of which the outer end of lever 6 may rest. It now rests on contact 5 ; hence it is evident that current must pass through all the resistance coils or grids. If it be moved to 4, coil A will be cut out; if moved to 3, coils A and B will be eliminated and so on, until only the "fixed resistance'' will be in use. That is all there is to the adjustable rheostat. They all operate on the same general principle, though there are several variations in the manner in which the amount of resistance may be changed.