Electrical circuits joule

It is important to bear in mind that an electrophoresis gel is an element in an electrical circuit and as such obeys the fundamental laws of electricity. Each gel has an intrinsic resistance, R, determined by the ionic strength of its buffer (R changes with time in discontinuous systems). When a voltage V is impressed across the gel, a current I flows through the gel and the external circuitry. Ohm s law relates these three quantities V = IR, where V is expressed in volts, I in amperes, and R in ohms. In addition, power P, in watts, is given by P = IV. The generation of Joule heat, H, is related to power by the mechanical equivalent of heat, 4.18 J/cal, so that H = (PI4.18) cal/sec. 

Joule heating Heat produced in an electric circuit by the flow of electricity. Power (J/s) = 12R, where / is the current (A) and R is the resistance (ohms). 

This equation can be nsed because electrical work can be calcnlated by multiplying the voltage by the amount of charge transported through the circuit (joules = volts x coulombs). The nF term in Equation (19.2) of the text nsed above represents the amonnt of charge. 

In an electric circuit, the quantity of charge flowing per second is called the current, i. The unit of current is the ampere. A 1 A equals 1 C/s. The potential difference, E, between two points in the cell is the amount of energy required to move the charged electrons between the two points. If the electrons are attracted from the first point to the second point, the electrons can do work. If the second point repels the electrons, work must be done to force them to move. Work is expressed in joules, J, and the potential difference, E, is measured in volts. The relationship between work and potential difference is ... 

Joule s Law - The rate of heat production by a steady current in any part of an electrical circuit that is proportional to the resistance and to the square of the current, or, the internal energy of an ideal gas depends only on Its temperature. 

In the context of resistive circuits and in light of conservation of energy and electrical potential. Joule s first law and Ohm s law are equivalent and derivable from each other, although they were discovered... 

In some applications it is necessary to introduce the idea of power. This is defined to be the rate at which energy is expended or work is done and is measured in watts (W). In SI units, a watt is defined to be one joule per second (J s ), equivalent to 10 erg s in cgs units cf. Table D.2. In electrical circuits one watt is equivalent to the product of one ampere by one volt. 

Power, P, defiaed as the rate at which work is performed, is expressed ia terms of energy divided by time and is most commonly given in units of horsepower, as for the power suppHed by mechanical devices such as diesel engines, or in the SI units of watts, especially when measuring electrical power. One horsepower is equivalent to the amount of power needed to lift 33,000 pounds (14,982 kg) one foot (30.5 cm) in one minute. One watt is equivalent to the power required to perform one joule of work per second. In a simple direct-current circuit where potential is represented by E ... 

The Joule-Brayton (JB) constant pressure closed cycle is the basis of the cyclic gas turbine power plant, with steady flow of air (or gas) through a compressor, heater, turbine, cooler within a closed circuit (Fig. 1.4). The turbine drives the compressor and a generator delivering the electrical power, heat is supplied at a constant pressure and is also rejected at constant pressure. The temperature-entropy diagram for this cycle is also... 

Direct current cardioversion is the process of administering a synchronized electrical shock to the chest. The purpose of DCC is to simultaneously depolarize all of the myocardial cells, resulting in interruption and termination of the multiple reentrant circuits and restoration of normal sinus rhythm. The initial energy level of the shock is 100 joules (J) if the DCC attempt is unsuccessful, successive cardioversion attempts maybe made at 200,300, and 360 J.14 Delivery of the shock is synchronized to the ECG by the cardioverter machine, such that the electrical charge is not delivered during... 

The reverse of the Seebeck effect is called the Peltier effect and results from flowing an electric current through the circuits of figure 9.1. If the junctions are initially at the same temperature, a temperature gradient will be developed for instance, in the case of figure 9.1a, one of the junctions will cool and the other will warm. Associated with this electric current there will also be a Joule (resistive) effect, so that the net power (P) produced at each junction is given by... 

The heat developed in a circuit by an electric current of I - 1 ampere flowing through a resistance of R, - 1 ohm (across a potential difference of V, - 1 volt) for a time t — 1 second is defined to be 1 ioule. One calorie is defined as equal to 4.1840 joules and corresponds very closely to the heat required to raise the temperature of 1 g of pure water from 14.5 to 15.5 C. More generally, the heat developed by current flow in a circuit is specified by... 

The heat transfer was originally measured in units of calories, where one calorie was defined as the quantity of energy required to raise one gram of pure water from 14.5 to 15.5 °C at one atmosphere. This definition has been supplanted by the introduction of the joule, which represents the energy specified by the conversion factor 1 cal = 4.184 joules. One joule is also equivalent to the energy developed in a circuit by an electric current of one ampere flowing through a resistance of one ohm (driven by a potential difference of one volt) in one second. 

By the principles of thermodynamics discussed in Chapter V., a galvanic cell will yield the maximum amount of work when the production of electricity takes place reversibly, that is to say, when the changes which take place both inside and outside the cell are completely reversed when an equally strong current is sent in the opposite direction through the cell. This can only occur when the current flowing through the cell is infinitely small, so that the irreversible production of Joule heat inside the cell is avoided. The electrode potential of the cell on open circuit (measured by the compensation method, for example) is therefore a measure of the maximum electrical work which the cell can do. It is also a measure of the chemical affinity of the reaction as defined on p. 318, Chapter IX. 

Joule s law states that an electric current produces in a circuit an amount of heat which is proportional to the square of the current intensity, to the resistance in the circuit, and to the duration of the current. The heat produced in the circuit is... 

---