Potential difference magnitude

Hall effect If a current (I) is passed through a conducting crystal in a direction perpendicular to that of an applied magnetic field (H), the conductor develops a potential (V) between the faces which are mutually perpendicular to both the direction of the current and the magnetic field. This is known as the Hall effect the magnitude of the potential difference is given by... 

Once current passes tluough the interface, the Galvani potential difference will differ from that expected from the Nemst equation above the magnitude of the difference is temied the overpotential, which is defined heiiristically as... 

Generai description. Galvanic corrosion refers to the preferential corrosion of the more reactive member of a two-metal pair when the metals are in electrical contact in the presence of a conductive fluid (see Chap. 16, Galvanic Corrosion ). The corrosion potential difference, the magnitude of which depends on the metal-pair combination and the nature of the fluid, drives a corrosion reaction that simultaneously causes the less-noble pair member to corrode and the more-noble pair member to become even more noble. The galvanic series for various metals in sea water is shown in Chap. 16, Table 16.1. Galvanic potentials may vary with temperature, time, flow velocity, and composition of the fluid. 

Consideration of the basic elements characteristic of the galvanic corrosion process, as discussed above, points to the principles of sound preventive techniques. Since a galvanic potential difference is the driving force for corrosion reducing the magnitude of this difference can reduce or prevent galvanic corrosion. 

If the projected pipeline is situated in an area with dc railway lines, rail/soil potential measurements should be carried out at crossing points and where the lines run parallel a short distance apart, particularly in the neighborhood of substations, in order to ascertain the influence of stray currents. Potential differences at the soil surface can give information on the magnitude of stray current effects in the vicinity of dc railway lines. It is recommended that with existing pipelines the measurements be recorded synchronously (see Section 15.5) and taken into account during design. 

An ideal (classical) electrostatic capacitor consists of two plane-parallel metal plates having surface areas S and a mutual distance 5, the gap being filled with air or a dielectric layer (the latter variety often is called a film capacitor). When a capacitor is charged (by applying an electrostatic potential difference A / between the two plates), electrical charges +Q m electron deficit) and Q (an efectron excess), which are equal in magnitude but opposite in sign, will accnmulate on the plates. The values of Q are proportional to the potential difference ... 

Galvanic corrosion is a frequent source of trouble on a large scale. Not only is the use of different metals in the same piece of equipment dangerous, but the effect of cold working may be sufficient to estabhsh potential differences of objectionable magnitude between different... 

If this EMF is compensated by an external electrical potential difference of the same magnitude and of opposite polarity, then no current flows and the system is at equilibrium. The phase equilibria of communicating species are... 

The student then added 10. mL of 1.0 M NaCl solution to an empty beaker. He then added one drop of 1.0 M AgN03 to the beaker and stirred well. Since there is an abundance of Cl in the beaker, and the amount of NaCl (10. mL) is magnitudes greater than the one drop of 1.0 M AgN03, it can be assumed that most of the Ag+(aq) will combine with the CT(aq) and that the concentration of the Cl (aq) will remain essentially 1.0 M. A silver metal electrode was immersed in this solution and connected through the salt bridge to the Zn I Zn2+ half-cell. The potential difference was measured as 0.91 volts. 

To gauge the magnitude of the thermoelectric power effect, the thermoelectric power coefficient is defined simply as the potential difference developed, dV, per unit temperature difference, dT ... 

Figure 8.8 In impedance analysis, a sinusoidally varying potential V is applied across a sample, and the time-dependent current / is measured as a function of the frequency co. The current induced in response to the varying potential will be out of phase, by a time lag 9, and of different magnitude.

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