Cinematographic annual : 1930 (1930)

Record Details:

Title:
Cinematographic annual : 1930
Date:
1930
Publisher:
Hollywood : The American Society of Cinematographers, Inc.
Volume:
Cinematographic annual : 1930
Leaf #:
000618
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
{"Media History Digital Library","Richard Koszarski","Jeff Joseph"}
Coordinator:
Media History Digital Library
Description:
Date Added:
March 21, 2024
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598 < 'IXKMATOGRAPHIC: ANNUAL Electricity Ohmic Resistance The resistance of a uniform electric conductor at o°, Centigrade, is given by the formula: R (in ohms) =» p L/A L = length of conductor in inches A = Cross-section in square inches p = Resistivity of conductor at o° C, values of which are given in the following table Table of Resistivities (Resistivity is the resistance in ohms between any two opposite faces of a I inch cube of the material. It is given in microhms or millionths of an ohm.)* Metal Resistivity at o° C. (in microhms) Aluminum (annealed) Aluminum (commercial) .... Aluminum bronze . Bismuth (compressed) Brass 1. 14 1.05 4.96 2.82 Copper (drawn) Copper (annealed) ....... German silver ..... ^ ... . Gold (annealed) Iron (wrought) Lead (compressed) Magnesium 0.637 0.625 8.23 0.803 3.82 7.68 1.72 Mercury Nickel (annealed) Platinum (annealed) Silver (annealed) Tin Tungsten 37.1 4.89 3.53 0.575 5.16 2. Zinc (pressed) 2.28 * This definition applies to English units and to the numerical values given in the table. In general, resistivity is the resistance of a unit cube. The resistance of a conductor at any temperature is (i+at8) R, Rr (i+ati) in which Ri = known resistance at a temperature ti degrees Centigrade R* = required resistance at a temperature U degrees Centigrade a = temperature coefficient of electrical resistance, the value of which is given for different metals in the following table.