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 #:
00046
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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28 RICHARDSON'S BLUEBOOK OF PROJECTION follows that if E (voltage) divided by R (resistance in ohms) equals I (amperes flowing), then I multipled by R must equal E; and E divided by I must equal R. E These equations are expressed as — = 1; IXR = E; R E — = R. It works out as follows: (109) If an incanI descent lamp bulb filament requires half an ampere at 110 volts to build up the required light value, what resistance of the filament is necessary to restrict current E flow to one-half ampere? The answer is — = R. Sub I E 110 stituting figures we have = 220 ohms. (110) I .5 If we reverse the problem, knowing the resistance in ohms and the voltage and wishing to ascertain the cur E 110 rent flow in amperes, we would have — = I or = .5 R 220 of an ampere. Again, knowing the resistance in ohms and the amperage, we would have 220 X .5 = 110 volts. This simple formula is the basis of many electrical calculations. Rule o' Thumb (111) In using Ohm's Law what is known as the "Rule o' Thumb" is a convenient assistant to memory. E It is simple. Write the formula — — . Cover the letter IR representing the quantity desired. What remains will provide the answer, thus : if we cover the R we see that E ■**M = R. If we cover the E we have I XR = E. If we cover the I we then have E '-* R = L In using this formula on projection circuits the upper letter must be written as E minus the arc voltage or "arc drop/'