Ampere_balance_1927.jpg
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Summary
Description Ampere balance 1927.jpg |
English:
A precision
Ampere balance
at the US
National Bureau of Standards
(now
NIST
that served as a standard for comparing
electric current
for the United States in 1927. This specific type was called a Rosa-Dorsey current balance. It consisted of a sensitive
laboratory balance
(top)
with one of its pans replaced by a coil of wire
(visible under balance)
, with a second stationary coil of wire below it. An unknown current is passed through the coils, causing the upper coil to be attracted to the lower coil, pulling the right arm of the balance down. Standard weights are put on the lefthand pan until the arms balance. The magnitude of the unknown current can be calculated from the weights and the dimensions of the coils. The accuracy of the Ampere balance was limited because it was dependent on the shape and rigidity of the wire coils. It was replaced as a standard of electric current in the 1960s by atomic standards, such as
Josephson junctions
.
|
Date | |
Source | Retrieved June 28, 2013 from Standards Yearbook, 1927 , miscellaneous publication No. 77, US National Bureau of Standards, Commerce Dept. printed by US Government Printing Office, Washington, p. 396, fig. 9 on Google Books |
Author | George K. Burgess, Director, National Bureau of Standards |
Licensing
Public domain Public domain false false |
This work is in the
public domain
in the United States because it is a
work prepared by an officer or employee of the United States Government as part of that person’s official duties
under the terms of
Title 17, Chapter 1, Section 105
of the
US Code
.
Note
: This only applies to original works of the Federal Government and not to the work of any individual
U.S. state
,
territory
, commonwealth, county, municipality, or any other subdivision. This template also does not apply to postage stamp designs published by the
United States Postal Service
since 1978
. (See §
313.6(C)(1)
of Compendium of U.S. Copyright Office Practices). It also does not apply to certain US coins; see
The US Mint Terms of Use
.
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https://creativecommons.org/publicdomain/mark/1.0/ PDM Creative Commons Public Domain Mark 1.0 false false