Batteries electrical work

In an electrochemical cell, electrical work is obtained from an oxidation-reduction reaction. For example, consider the process that occurs during the discharge of the lead storage battery (cell). Figure 9.3 shows a schematic drawing of this cell. One of the electrodes (anode)q is Pb metal and the other (cathode) is Pb02 coated on a conducting metal (Pb is usually used). The two electrodes are immersed in an aqueous sulfuric acid solution. 

Figure 9.3 The lead storage battery. The key to obtaining electrical energy from a redox chemical reaction is to physically separate the two half-cell reactions so that electrons are transferred from the anode through an external circuit to the cathode. In the process, electrical work is accomplished.

Electrical work is usually performed in an electrical circuit, as shown schematically in Fig. 3.7. The circuit consists of a voltage source (e.g., a battery) E connected through a resistance R with circulating current I. These quantities are related by Ohm s law,... 

Equations (8.55), (8.57) make it easy to see the connection between cell potential and reaction spontaneity. When is positive (AG < 0), the cell reaction is spontaneous, allowing useful electrical work to be withdrawn (i.e., the battery is draining ). Conversely, when is negative (AG > 0), the cell reaction is spontaneous, requiring input work from the surroundings (i.e., the battery is charging ). When = 0 (AG = 0), the cell reaction is at equilibrium, and, in accordance with (8.27d), the Nernst equation reduces to... 

One of the oldest and most important applications of electrochemistry is to the storage and conversion of energy. You already know that a galvanic cell converts chemical energy to work similarly, an electrolytic cell converts electrical work into chemical free energy. Devices that carry these conversions out on a practical scale are called batteries1. In ordinary batteries the chemical components are contained within the device itself. If the reac-tantsare supplied from an external source as they are consumed, the device is called a fuel cell. 

Clearly, in galvanic cells of practical interest (i.e. in batteries and fuel cells), the voltage of operation U has to be a compromise. It must be smaller than E for obtaining an adequate current flow. On the other hand, it has to be close to E in order to recover as much as possible electric work, W. 

A battery harnesses a chemical reaction to extract energy in the form of useful electrical work. 

A 6.00-V battery delivers a steady current of 1.25 A for a period of 1.50 hours. Calculate the total charge Q, in coulombs, that passes through the circuit and the electrical work done by the battery. 

AFV penetration has been most successful in markets that are small, well-defined, and with limited competition, such as in the transit bus, garbage truck, school bus, and taxi markets. Yet these are the same markets least likely to catalyze broader market penetration. Some have suggested alternative fuels, especially battery electric vehicles, may be able to carve out new market niches as "disruptive technologies" that serve unmet consumer needs (Christensen, 1997). Yet the size, scale, and diversity of the existing transportation market works against this by providing a huge portfolio of options for almost every consumer transportation need. 

In thermodynamics, work has a broader meaning that includes mechanical work (for example, a crane lifting a steel beam), electrical work (a battery supplying electrons to light the bulb of a flashlight), and so on. In this section we will concentrate on mechanical work in Chapter 19 we will discuss the nature of electrical work. 

American Coalition of Traffic Safety (ACTS), presented at the Ad Hoc Electric Vehicle Battery Readiness Working Group, ACTS Foundation, 1110 Glebe Rd., Suite 1020, Arlington, VA, 22201, January 20-21,1994. 

As alluded to above, chemical systems undergoing change (i.e., in which reactions occur) can do various kinds of work. For instance, batteries can do electrical work. While undergoing these reactions, the chemical system invariably has some change in volume, because it is most unlikely that the reaction products would have exactly the same volume as the reactants. This change in volume AV takes place under some ambient pressure P, so that PAV work is done during the reaction regardless of whether any other kind of work is done or not—if the reaction is to take place. 

In some of his experiments. Joule used electrical work rather than mechanical work. To achieve the same effect as in Problem 2.4(a), for what duration would electrical work have to be provided to the calorimeter, if the current originated from a 100-volt battery and it encountered a 1000-ohm resistance ... 

The tendency of many electrochemical reactions to move toward complete formation of products presents a significant challenge in the case of corrosion, but it also provides opportunities for using these reactions positively. The most familiar example of this is the battery, a cell or series of cells that generates an electric current. Batteries are composed of many different materials and find many uses, but they all share one common property—they provide a means by which we harness the electrical work of a galvanic cell and use it productively. We will see, however, that batteries have something else in common—they are susceptible to corrosion. So even when we intend to put electrochemistry to work for us, we still need to think about corrosion. Let s develop some ideas about batteries in general as we consider some specific examples. 

In thermodynamics, work has a broader meaning that includes mechanical work (for example, a crane lifting a steel beam), electrical work (a battery supplying electrons... 

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