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Title: ELECTROMOTIVE FORCE, EMF (CELLS)

Abstract

The voltage or electric potential difference across the terminals of a cell when no current is drawn from it. The emf of a cell is the sum of the electric potential differences (PDs) produced by a separation of charges (electrons or ions) that can occur at each phase boundary (or interface) in the cell. The magnitude of each PD depends on the chemical nature of the two contacting phases. Thus, at the interface between two different metals, some electrons will have moved from the metal with a higher free energy of electrons to the metal with a lower free energy of electrons. The resultant charge separation will produce a PD (just as charge separation produces a voltage across a capacitor) that, at equilibrium, exactly opposes further electron flow. Similarly, PDs can be produced when electrons partition across a metal/solution interface or metal/solid interface, and when ions partition across a solution/membrane/solution interface.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Lab., Upton, NY (US)
Sponsoring Org.:
USDOE Office of Energy Research (ER) (US)
OSTI Identifier:
760971
Report Number(s):
BNL-65847; KC030101
R&D Project: AS002CSD; KC030101; TRN: AH200035%%46
DOE Contract Number:
AC02-98CH10886
Resource Type:
Miscellaneous
Resource Relation:
Other Information: PBD: 16 Sep 1998; Related Information: In: Encyclopedia of Science and Technology, vp.
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ELECTRIC POTENTIAL; ELECTROMOTIVE FORCE; FREE ENERGY; ELECTROLYTIC CELLS; ELECTRON TRANSFER

Citation Formats

Archer, M.D., and Feldberg, S.W.. ELECTROMOTIVE FORCE, EMF (CELLS). United States: N. p., 1998. Web.
Archer, M.D., & Feldberg, S.W.. ELECTROMOTIVE FORCE, EMF (CELLS). United States.
Archer, M.D., and Feldberg, S.W.. 1998. "ELECTROMOTIVE FORCE, EMF (CELLS)". United States. doi:. https://www.osti.gov/servlets/purl/760971.
@article{osti_760971,
title = {ELECTROMOTIVE FORCE, EMF (CELLS)},
author = {Archer, M.D. and Feldberg, S.W.},
abstractNote = {The voltage or electric potential difference across the terminals of a cell when no current is drawn from it. The emf of a cell is the sum of the electric potential differences (PDs) produced by a separation of charges (electrons or ions) that can occur at each phase boundary (or interface) in the cell. The magnitude of each PD depends on the chemical nature of the two contacting phases. Thus, at the interface between two different metals, some electrons will have moved from the metal with a higher free energy of electrons to the metal with a lower free energy of electrons. The resultant charge separation will produce a PD (just as charge separation produces a voltage across a capacitor) that, at equilibrium, exactly opposes further electron flow. Similarly, PDs can be produced when electrons partition across a metal/solution interface or metal/solid interface, and when ions partition across a solution/membrane/solution interface.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1998,
month = 9
}

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  • The thermally induced flux motion and the elemental pinning force, fp, for Nb thin films (1000-5000A) were measured for applied magnetic fields ranging from 0.3 to 7.5G, and temperatures from 4.22 to 5.72 K. The magnitude of f{sub p} (H,d,T) ranged from 10{sup {minus}12} to 10{sup {minus}11} N/m which is approximately 5 orders of magnitude smaller than Lorentz force depinning measurements made on Nb for the high field regime (flux line lattice), as well as the low field regime (isolated essentially non-interacting fluxoids). Some of these results are similar to the works of Huebener, et al, who first found amore » large discrepancy between the transport current method (J {times} B) and the thermal method, S{del}T, when calculating the pinning force on a flux line lattice structure. A model was proposed to explain the discrepancy in terms of an electron-scattering effect at or near the grain boundaries and extending into the grains which produces a channeling effect. The data exhibited a magnetic field threshold, below which there is no flux motion for the temperature range studied. The value of the minimum required applied field necessary for flux motion increases with increasing thickness.« less
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