Mechanical Engineering Handbook Frank Kreith Pdf FilePassive sign convention Wikipedia. Illustration of the reference directions of the current i, voltage v, and power p variables used in the passive sign convention. If positive current is defined as flowing into the terminal which is defined to have positive voltage, then positive power represents electric power flowing into the device big arrow. In electrical engineering, the passive sign convention PSC is a sign convention or arbitrary standard rule adopted universally by the electrical engineering community for defining the sign of electric power in an electric circuit. The convention defines electric power flowing out of the circuit into an electrical component as positive, and power flowing into the circuit out of a component as negative. Prince Of Persia Hd S60v5 there. So a passive component which consumes power, such as an appliance or light bulb, will have positive power dissipation, while an active component, a source of power such as an electric generator or battery, will have negative power dissipation. This is the standard definition of power in electric circuits it is used for example in computer circuit simulation programs such as SPICE. To comply with the convention, the direction of the voltage and current variables used to calculate power and resistance in the component must have a certain relationship the current variable must be defined so positive current enters the positive voltage terminal of the device. These directions may be different from the directions of the actual current flow and voltage. The conventioneditThe passive sign convention states that in components in which the conventional current variable i is defined as entering the device through the terminal which is positive as defined by the voltage variable v,24 the power p and resistance r are given by567pvidisplaystyle pvi,     and     rvidisplaystyle rvi,In components in which the current i is defined so positive current enters the device through the negative voltage terminal, power and resistance are given bypvidisplaystyle p vi,   and   rvidisplaystyle r viqquad ,With these definitions, passive components loads will have p 0 and r 0, and active components power sources will have p lt 0 and r lt 0. ExplanationeditLoad passive componentPower source active componentActive and passive componentseditIn electrical engineering, power represents the rate of electrical energy flowing into or out of a given component or control volume. Power is a signed quantity negative power just represents power flowing in the opposite direction from positive power. From the standpoint of power flow, electrical components in a circuit can be divided into two types 2In a load or passive component, such as a light bulb, resistor, or electric motor, electric current flow of positive charges moves through the device under the influence of the electric field. E in the direction of lower electric potential, from the positive terminal to the negative. So work is done by the charges on the component potential energy flows out of the charges and electric power flows from the circuit into the component, where it is converted to some other form of energy such as heat or mechanical work. In a source or active component, such as a battery or electric generator, current is forced to move through the device in the direction of greater electric potential, from the negative to the positive voltage terminal. This increases the potential energy of the electric charges, so electric power flows out of the component into the circuit. Work must be done on the moving charges by some source of energy in the component, to make them move in this direction against the opposing force of the electric field. E. Some components can be either a source or a load, depending on the voltage or current through them. For example, a rechargeable battery acts as a source when it is used to produce power, but as a load when it is being recharged. Since it can flow in either direction, there are two possible ways to define electric power two possible reference directions either power flowing into the circuit, or power flowing out of the circuit, can be defined as positive. Whichever is defined as positive, the other will be negative. The passive sign convention arbitrarily defines power flowing out of the circuit into the component as positive,2 so passive components have positive power flow. In an AC alternating current circuit the current and voltage switch direction periodically, but the definitions above still apply in passive components the current flows from the positive terminal to the negative, while in active components it flows the other direction. Reference directionseditThe power flow p and resistancer of an electrical component are related to the voltage v and current i variables by the defining equation for power and Ohms law pvi1displaystyle pviqquad qquad qquad ,1,rvi2displaystyle rviqquad qquad qquad 2,Like power, voltage and current are signed quantities. The current flow in a wire has two possible directions, so when defining a current variable i the direction which represents positive current flow must be indicated, usually by an arrow on the circuit diagram. This is called the reference direction for current i. If the actual current is in the opposite direction, the variable i will have a negative value. Similarly in defining a variable v representing the voltage between two terminals, the terminal which represents the positive side must be specified, usually with a plus sign. This is called the reference direction for voltage v. If the terminal marked positive actually has a lower voltage than the other one, then the variable v will have a negative value. To understand the passive sign convention, it is important to distinguish the reference directions of the variables, v and i, which can be assigned at will, from the direction of the actual voltage and current, which is determined by the circuit. The idea of the PSC is that by assigning the reference direction of variables v and i in a component with the right relationship, the power flow in passive components calculated from Eq. It is not necessary to know whether a component produces or consumes power when analyzing the circuit reference directions can be assigned arbitrarily, directions to currents and polarities to voltages, then the PSC is used to calculate the power in components. If the power comes out positive, the component is a load, converting electric power to some other kind of power. If the power comes out negative, the component is a source, converting some other form of power to electric power. Sign conventionseditThe above discussion shows that choosing the relative direction of the voltage and current variables in a component determines the direction of power flow that is considered positive. The reference directions of the individual variables are not important, only their relation to each other. There are two choices Passive sign convention Defining the current variable as entering the positive terminal means that if the voltage and current variables have positive values, current flows from the positive to the negative terminal, doing work on the component, as occurs in a passive component. Mechanical Engineering Handbook Frank Kreith Pdf Printer' title='Mechanical Engineering Handbook Frank Kreith Pdf Printer' />Mechanical Engineering Handbook Frank Kreith Pdf To WordIn physics, a free surface is the surface of a fluid that is subject to zero parallel shear stress, such as the boundary between two homogeneous fluids, for example. Kreith, F. Boehm, R. F. et. al. Heat and Mass Transfer Mechanical Engineering Handbook Ed. Games American Army. Frank Kreith Boca Raton CRC Press LLC, 1999. In electrical engineering, the passive sign convention PSC is a sign convention or arbitrary standard rule adopted universally by the electrical engineering. International Journal of Engineering Research and Applications IJERA is an open access online peer reviewed international journal that publishes research.