Potential energy electromotive force

Young s modulus standard electrode potential standard electromotive force half-wave potential first-order elimination second-order elimination Arrhenius or activation energy... 

Just as, in hydrodynamics, the energy of falling water is determined not only by the amount of water that falls, but also by the height of fall, so also in electricity, the electrical energy involves the two factors, amount of electridty, and fall of potential or electromotive force. This latter ctor constitutes the driving force, and its measurement is of the utmost importance. 

Electric pofcTidfff, ), potential difference, or electromotive force (emf, E, e) have units of volts and refer to the energy change when a charge is moved from one point to another m an electric field. 

Wagner pioneered the use of solid electrolytes for thermochemical studies of solids [62], Electrochemical methods for the determination of the Gibbs energy of solids utilize the measurement of the electromotive force set up across an electrolyte in a chemical potential gradient. The electrochemical potential of an electrochemical cell is given by ... 

While the voltage of the cell represents the potential difference between the two terminals of the battery, in reality it relates to the separation in energy between the two half-cells. We call this separation the emf where the initials derive from the archaic phrase electromotive force. An emf is defined as always being positive. 

An electrical potential difference between the electrodes of an electrochemical cell (called the cell potential) causes a flow of electrons in the circuit that connects those electrodes and therefore produces electrical work. If the cell operates under reversible conditions and at constant composition, the work produced reaches a maximum value and, at constant temperature and pressure, can be identified with the Gibbs energy change of the net chemical process that occurs at the electrodes [180,316]. This is only achieved when the cell potential is balanced by the potential of an external source, so that the net current is zero. The value of this potential is known as the zero-current cell potential or the electromotive force (emf) of the cell, and it is represented by E. The relationship between E and the reaction Gibbs energy is given by... 

From the energy diagram shown in Fig. 10-33, the operating cell voltage, V,, is obtained, as expressed in Eqn. 10-60, by subtracting from the electromotive force AEph the potential barrier of the space charge layer, the cathodic overvoltage t h, and the iR drop in the electrolyte ... 

Figure 10-34 shows the energy diagram of an operating photovoltaic cell which consists of a photoexcited anode of n-type semiconductor and a photoexdted cathode of p-lype semiconductor. The electromotive force, of this type of photovoltaic cell approximately equals the difference between the flat band potential of the n-type anode and the flat band potential fEg, of the p-type cathode as shown in Eqn. 10-62 ... 

In a redox reaction, the energy released in a reaction due to movement of charged particles gives rise to a potential difference. The maximum potential difference is called the electromotive force (FMF), E, and the maximum electric work, W, is the product of charge q in Coulombs (C), and the potential NE in volts or FMF ... 

Because, as we have already seen, the standard potential of hydrogen is zero, the electromotive force of the galvanic cell (eq. 8.161) directly gives the value of the standard potential for the Zn,Zn redox couple. Table 8.14 lists the standard potentials for various aqueous ions. The listed values are arranged in decreasing order and are consistent with the standard partial molal Gibbs free energies of table 8.13. 

The cell potential E (also called the cell voltage or electromotive force) is an electrical measure of the driving force of the cell reaction. Cell potentials depend on temperature, ion concentrations, and gas pressures. The standard cell potential E° is the cell potential when reactants and products are in their standard states. Cell potentials are related to free-energy changes by the equations AG = —nFE and AG° = —mFE°, where F = 96,500 C/mol e is the faraday, the charge on 1 mol of electrons. 

An electrochemical cell generates a potential difference E. (The symbol E, commonly used in electrochemistry, refers to electromotive force, an archaic term for potential difference.) The electrical work done when n moles of electrons is passed by the cell can be found using Eq. (15-1), w = -nFE. It can be shown that the electrical work done by an electrochemical cell, at constant temperature and pressure, is equal to the change in Gibbs free energy of the cell components,... 

For biochemical reactions undergoing oxidation-reduction (redox reaction), the free energy change is related to the electromotive force (emf) or redox potential (AEQ of the reaction ... 

This process leads to the development of a voltage difference between anode and cathode and when the external circuit is open , this potential difference is the electromotive force (the e.m.f.) of the cell. When there is an electrical load in the external circuit, for example a motor, then a current will flow and electrochemical energy is converted into mechanical energy. 

Unfortunately, there is not enough current produced to do any work, but there is enough to measure (1 to 7 millivolts). This rise in potential energy is called the emf or electromotive force. 

If the difference in energy level between a free ion and one bound to the surface of the metal is Y, and the difference in level between a free ion and a hydrated one is W, then the difference in energy level between the hydrated ion, and the ion at the surface of the metal is W—Y. The energy level of the ions in solution depends, however, on the concentration of these ions this produces the well-known effect of concentration on electromotive force. Gurney gives9 the strength of the double layer, i.e. the difference in electrostatic potential set up between metal a and electrolyte s, as... 

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