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A voltage greater than that at which a device or circuit is designed to operate. Also known as overpotential.
The amount by which the applied voltage exceeds the Geiger threshold in a radiation counter tube.
(physical chemistry)
The difference between electrode potential under electrolysis conditions and the thermodynamic value of the electrode potential in the absence of electrolysis for the same experimental conditions. Also known as overpotential.



in electrochemistry, the difference between the equilibrium (with respect to the composition of the electrode solution) value of electrode potential and the value of the electrode potential when the electrode is polarized by an external current. When the departure from equilibrium is noticeable, the relation between the overvoltage η and the density i of the polarizing current is usually given by the Tafel equation η = a + b log10i where a and b are empirical constants. Overvoltage depends on the temperature, the nature of the electrode material, and the composition of the solution.

Overvoltage is necessary for the acceleration of a desired electrode reaction. If the rate of the electrode reaction is determined by the rate of the electrochemical stage proper, which involves charge transfer, then overvoltage amplifies the electric field acting on the particles undergoing discharge, with a resulting lower discharge activation energy: Since the electric field is to a great extent due to the structure of the electrical double layer, overvoltage turns out to be dependent on the concentration of the foreign electrolyte and the adsorbed materials, which affect the distribution of potential in the double layer.

Overvoltage has some positive apects; for example, the action of many inhibitors of metal corrosion is based on an increase in overvoltage. At the same time, overvoltage in industrial electrolysis inevitably involves additional power consumption and leads to increased production costs.


Kinetika elektrodnykh protsessov. Moscow, 1952. (Collective of authors under the direction of A. N. Frumkin.)
Skorchelletti, V. V. Teoreticheskaia elektrokhimiia. Leningrad, 1959.
Antropov, L. I. Teoreticheskaia elektrokhimiia, 2nd ed. Moscow, 1969.


References in periodicals archive ?
Silicon Valley-based Kinetic Technologies announced the launch of KTS1670, the latest addition to its ever-growing over-voltage protection portfolio.
Using the ADA4177-2 at the front of the signal chain minimizes the impact of these events by filtering out the EMI at the input to the op amp or limiting the in-rush current of an over-voltage event to a safe level.
A higher level of over-voltage protection in a robust single-chip design.
This can help designers incorporate the appropriate precautions, such as enclosures for sensitive equipment or special diodes that would 'short out' rather than cause an over-voltage inside the equipment.
a wholly owned subsidiary of IXYS Corporation (NASDAQ: IXYS), announced the immediate availability of the CPC1593, the first in a new family of triple stage protection solid state relays (SSRs) that incorporate load current-limiting with over-voltage protection and thermal management.
The -30 V VDS of the Vishay Siliconix device released today provides the headroom needed for over-voltage spikes, while its 12 V VGS enables lower on-resistance ratings of -3.
The new 30-W modules offer unique functional features that include latch-off output over-voltage protection (OVP) to help prevent damage to the high value digital and analog loads as a result of an over-voltage condition.
The series, which accepts a 90-264 V universal input, features output over-voltage, overload, and short circuit protections.
Features include [less than or equal to] 300-mW low power consumption, [less than or equal to] 2-mV p-p ripple, high stability, 0 to 100% programmable output voltage, over-voltage protection and voltage monitoring.
Transient voltage suppression diodes are designed to suppress over-voltage transients induced by electrically fast transients, inductive load switching, and lightning.
Improperly installed batteries, hot-plug transients, faulty connections, and reversible third party USB chargers can all generate a dangerous reverse bias or reverse transient situation as well as over-voltage spikes.
Features include parallel operation support, output over-voltage, low-voltage and over-current protection, an output over-voltage alarm, simultaneous start-up and start-up delay, and remote ON/OFF.