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qr code vb.net library Or, using eq. (13), eq. (15) becomes P RI I, so that P I 2R 17 in .NET
Or, using eq. (13), eq. (15) becomes P RI I, so that P I 2R 17 Code 128 Code Set C Scanner In Visual Studio .NET Using Barcode Control SDK for .NET framework Control to generate, create, read, scan barcode image in VS .NET applications. Generating Code 128B In .NET Using Barcode maker for .NET framework Control to generate, create Code 128 Code Set C image in Visual Studio .NET applications. Equations (11) through (17) should all be committed to memory, because they are of such fundamental importance. For our convenience, they are summarized below, where V is potential di erence in volts, I is current in amperes, R is resistance in ohms, and power is in watts. OHM S LAW: POWER: V RI P VI I V=R P I R Code128 Recognizer In .NET Framework Using Barcode scanner for VS .NET Control to read, scan read, scan image in .NET framework applications. Barcode Drawer In VS .NET Using Barcode printer for .NET Control to generate, create barcode image in .NET framework applications. R V=I P V 2 =R
Bar Code Recognizer In VS .NET Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in VS .NET applications. Create Code 128 Code Set B In C# Using Barcode generator for Visual Studio .NET Control to generate, create Code 128A image in Visual Studio .NET applications. Problem 8 In Fig. 22, if V 48 volts and R 6 ohms, what current will ow Problem 9 In Problem 8, nd the power output of the battery using eqs. (15), (16), and (17). Problem 10 If the power input to a 75ohm resistance is known to be 18 watts, what current is owing ANSI/AIM Code 128 Generator In Visual Studio .NET Using Barcode printer for ASP.NET Control to generate, create Code 128A image in ASP.NET applications. Code 128 Code Set B Creation In Visual Basic .NET Using Barcode creation for .NET Control to generate, create Code128 image in .NET applications. CHAPTER 2 Electric Current. Ohm s Law
Paint Bar Code In VS .NET Using Barcode generator for .NET framework Control to generate, create barcode image in .NET applications. Paint Code 39 Full ASCII In Visual Studio .NET Using Barcode creation for VS .NET Control to generate, create Code39 image in VS .NET applications. Some Notes on Temperature Effects
Making 1D In VS .NET Using Barcode creation for .NET framework Control to generate, create Linear Barcode image in .NET applications. Leitcode Generation In .NET Framework Using Barcode generation for Visual Studio .NET Control to generate, create Leitcode image in VS .NET applications. In devices such as electric heaters, irons, and toasters, the basic purpose is simply to develop a required amount of heat in the resistance wire used in such devices. In most applications, however, especially in electronics, resistance is not used in a circuit to develop heat, but is used for other purposes. The heat developed in resistance is, therefore, in most applications an undesired e ect. The principal reasons why this is true are as follows. 1. The resistance of a given length of a given type of wire depends, to some extent, upon the temperature of the wire. Thus, as the temperature of a wire increases, due to increased heat input, its resistance also tends to increase, and this is generally an undesirable e ect. Excessive heat generation adversely a ects the operation of other components in a circuit, and tends to cause physical deterioration of the resistor* itself. UCC.EAN  128 Drawer In C#.NET Using Barcode generator for .NET framework Control to generate, create UCC  12 image in VS .NET applications. UPC Symbol Generator In ObjectiveC Using Barcode generation for iPad Control to generate, create UPC A image in iPad applications. Let us discuss items (1) and (2) in more detail. To begin, it should be pointed out that the four principal factors that determine the resistance of a wire conductor are (a) the length L of the wire, (b) the crosssectional area A of the wire, (c) the material of which the wire is made, (d) the temperature T of the wire. Printing Bar Code In C# Using Barcode generation for VS .NET Control to generate, create bar code image in VS .NET applications. Data Matrix Drawer In None Using Barcode creation for Software Control to generate, create ECC200 image in Software applications. Let us deal with the rst three items rst. Experiment proves that the resistance R of a wire conductor is directly proportional to the length L and inversely proportional to the crosssectional area A, a fact we show mathematically by writing R L A 18 Reading Bar Code In VS .NET Using Barcode scanner for .NET Control to read, scan read, scan image in VS .NET applications. Encode EAN13 In None Using Barcode generator for Software Control to generate, create EAN13 image in Software applications. where R is the resistance in ohms, L is the length in meters, A is the crosssectional area in square meters, and where the proportional constant (the Greek letter rho ) is called the resistivity ( ree sis TIV ity ), whose value depends upon the material the wire is made of and the temperature T of the wire. Note that, from eq. (18), we have RA ohms meters 2 ohms meters L meters Make Bar Code In .NET Framework Using Barcode printer for ASP.NET Control to generate, create bar code image in ASP.NET applications. ANSI/AIM Code 128 Generator In C# Using Barcode creation for Visual Studio .NET Control to generate, create Code128 image in VS .NET applications. thus showing that resistivity has the dimensions ohms times meters, or ohm m, as it is usually written. As mentioned above, the value of depends on the kind of metal the wire is made of, and the temperature T of the wire. It is found that the resistivity of metals increases linearly with temperature over a wide range of temperature, and this fact is expressed in the form 0 1 0 T T0 19 * A device made solely to introduce resistance into a circuit is called a resistor ( ree SIS tor ). Thus, a 100 ohm, wirewound resistor is a device constructed of wire having 100 ohms of resistance. where
CHAPTER 2 Electric Current. Ohm s Law
resistivity of the given metal at any temperature T8C, 0 resistivity of the given metal at the standard reference temperature of T0 208C, 0 the temperature coe cient of resistance of the metal at 208C. The values of 0 and 0 ( alpha sub zero ) have been found experimentally, a short table of values being given below. 0 (ohm m) Silver Copper Aluminum Tungsten Constantan (1.59)10 (1.75)10 8 (2.83)10 8 (5.50)10 8 (49.0)10 8 0 (per 8C) (3.75)10 3 (3.80)10 3 (4.03)10 3 (4.70)10 3 (0.01)10 3 Note 1: Constantan is an alloy of 45% nickel and 55% copper having, as the table shows, a high value of resistivity and a very low value of temperature coe cient. Note 2: In some wire tables a unit of length called the mil is used, where 1 mil 0.001 inch. A circular mil is de ned as the area of a circle 1 mil in diameter. Let us next consider the power rating of a resistor, using, as a convenient example, a 100ohm resistor. Suppose, for example, that we are dealing with an application in which the resistor must carry a current of, say, 0.8 amperes. Then, by eq. (17), the power input to the resistor will be P I 2 R 64 watts, which is 64 joules of work per second. Since 1 calorie 4.186 joules,* we have 64=4:186 15:289 calories of heat will be developed in the resistor each second. We thus have a problem in heat transfer, because if the heat generated in the resistor is not transferred away fast enough the temperature of the resistor will continue to rise until it is destroyed. The ability of a resistor to dissipate heat depends greatly upon the amount of exposed surface area the resistor has. Thus, resistors that must dissipate relatively large amounts of heat must be made physically larger than resistors that must dissipate only a relatively small amount of heat. The amount of heat that a given resistor can safely dissipate also depends, of course, on the temperature of the surrounding (ambient) air, and whether the ow of air is by natural convection or is driven by a fan or blower. Resistors can be purchased in values of resistance from less than 1 ohm to several megohms ( 1 megohm being 1 million ohms), and in power rating from 1 watt to several 4 hundred watts. When specifying the power rating of a resistor, the manufacturer will also state the maximum temperature of ambient air for which the rating is valid. For example, a manufacturer might state that the power rating of a certain resistor is 5 watts at 308C ambient, and an equipment designer must keep this in mind. Resistors that must dissipate more than 2 or 3 watts are generally of the wirewound type, consisting of resistance wire, of low temperature coe cient, wound on a ceramic tube.

