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barcode in vb.net 2005 Power and the watt in Software
Power and the watt QR Code Scanner In None Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications. Making QR Code In None Using Barcode generation for Software Control to generate, create Quick Response Code image in Software applications. Whenever current flows through a resistance, heat results. This is inevitable. The heat can be measured in watts, abbreviated W, and represents electrical power. Power can be manifested in many other ways, such as in the form of mechanical motion, or radio waves, or visible light, or noise. In fact, there are dozens of different ways that power can be dissipated. But heat is always present, in addition to any other form of power in an electrical or electronic device. This is because no equipment is 100percent efficient. Some power always goes to waste, and this waste is almost all in the form of heat. QR Code JIS X 0510 Scanner In None Using Barcode scanner for Software Control to read, scan read, scan image in Software applications. Denso QR Bar Code Creation In Visual C#.NET Using Barcode encoder for .NET Control to generate, create QR Code image in .NET applications. 30 Electrical units
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Drawing QR Code JIS X 0510 In VB.NET Using Barcode generator for VS .NET Control to generate, create Denso QR Bar Code image in Visual Studio .NET applications. Paint Bar Code In None Using Barcode generator for Software Control to generate, create barcode image in Software applications. Look again at the diagram of Fig. 24. There is a certain voltage across the resistor, not specifically given in the diagram. There s also a current flowing through the resistance, not quantified in the diagram, either. Suppose we call the voltage E and the current I, in volts and amperes, respectively. Then the power in watts dissipated by the resistance, call it P, is the product E I. That is: P EI. This power might all be heat. Or it might exist in several forms, such as heat, light and infrared. This would be the state of affairs if the resistor were an incandescent light bulb, for example. If it were a motor, some of the power would exist in the form of mechanical work. If the voltage across the resistance is caused by two flashlight cells in series, giving 3 V, and if the current through the resistance (a light bulb, perhaps) is 0.1 A, then E 3 and I 0.1, and we can calculate the power P, in watts, as: (watts) EI 3 0.1 0.3 W UPC Code Drawer In None Using Barcode generation for Software Control to generate, create UPCA image in Software applications. Code 128C Creation In None Using Barcode maker for Software Control to generate, create Code128 image in Software applications. Suppose the voltage is 117 V, and the current is 855 mA. To calculate the power, we must convert the current into amperes; 855 mA 855/1000 0.855 A. Then P (watts) 117 0.855 100 W EAN13 Creator In None Using Barcode drawer for Software Control to generate, create EAN13 image in Software applications. DataMatrix Creation In None Using Barcode encoder for Software Control to generate, create Data Matrix ECC200 image in Software applications. AM FL Y
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Bar Code Printer In None Using Barcode creator for Online Control to generate, create bar code image in Online applications. Scan Barcode In Visual Basic .NET Using Barcode Control SDK for .NET framework Control to generate, create, read, scan barcode image in Visual Studio .NET applications. Energy and the watt hour 31 You will often hear about milliwatts (mW), microwatts ( W), kilowatts (kW) and megawatts (MW). You should, by now, be able to tell from the prefixes what these units represent. But in case you haven t gotten the idea yet, you can refer to Table 2 2. This table gives the most commonly used prefix multipliers in electricity and electronics, and the fractions that they represent. Thus, 1 mW 0.001 W; 1 W 0.001 mW 0.000001 W; 1 kW 1,000 W; and 1 MW 1,000 kW 1,000, 000 W. Scanning EAN / UCC  13 In None Using Barcode decoder for Software Control to read, scan read, scan image in Software applications. Bar Code Generator In None Using Barcode drawer for Excel Control to generate, create bar code image in Microsoft Excel applications. Table 22. Common prefix multipliers.
Barcode Encoder In Java Using Barcode generation for BIRT Control to generate, create barcode image in Eclipse BIRT applications. Data Matrix 2d Barcode Drawer In ObjectiveC Using Barcode encoder for iPhone Control to generate, create Data Matrix ECC200 image in iPhone applications. Prefix piconanomicromillikilomegagigateraFraction 0.000000000001 (onetrillionth) 0.000000001 (onebillionth) 0.000001 (onemillionth) 0.001 (onethousandth) 1000 1,000,000 1,000,000,000 (one billion) 1,000,000,000,000 (one trillion) Sometimes you need to use the power equation to find currents or voltages. Then you should use I P/E to find current, or E P/I to find power. It s easiest to remember that P EI (watts equal voltamperes), and derive the other equations from this by dividing through either by E (to get I) or by I (to get E). Energy and the watt hour
There is an important difference between energy and power. You ve probably heard the two terms used interchangeably, as if they mean the same thing. But they don t. Energy is power dissipated over a length of time. Power is the rate at which energy is expended. Physicists measure energy in joules. One joule is the equivalent of one watt of power, dissipated for one second of time. In electricity, you ll more often encounter the watt hour or the kilowatt hour. As their names imply, a watt hour, abbreviated Wh, is the equivalent of 1 W dissipated for an hour (1 h), and 1 kilowatt hour (kWh) is the equivalent of 1 kW of power dissipated for 1 h. An energy of 1 Wh can be dissipated in an infinite number of different ways. A 60watt bulb will burn 60 Wh in an hour, or 1 Wh per minute. A 100W bulb would burn 1 Wh in 1/100 hour, or 36 seconds. A 6watt Christmas tree bulb would require 10 minutes (1/6 hour) to burn 1 Wh. And the rate of power dissipation need not be constant; it could be constantly changing. 32 Electrical units Figure 26 illustrates two hypothetical devices that burn up 1 Wh of energy. Device A uses its power at a constant rate of 60 watts, so it consumes 1 Wh in a minute. The power consumption rate of device B varies, starting at zero and ending up at quite a lot more than 60 W. How do you know that this second device really burns up 1 Wh of energy You determine the area under the graph. This example has been chosen because figuring out this area is rather easy. Remember that the area of a triangle is equal to half the product of the base length and the height. This second device is on for 72 seconds, or 1.2 minute; this is 1.2/60 0.02 hour. Then the area under the curve is 1/2 100 0.02 1 Wh. 26 Two devices that burn 1 Wh of energy. Device A dissipates a constant power; device B dissipates a changing amount of power. When calculating energy values, you must always remember the units you re using. In this case the unit is the watt hour, so you must multiply watts by hours. If you multiply watts by minutes, or watts by seconds, you ll get the wrong kind of units in your answer. That means a wrong answer! Sometimes, the curves in graphs like these are complicated. In fact, they usually are. Consider the graph of power consumption in your home, versus time, for a whole day. It might look something like the curve in Fig. 27. Finding the area under this curve is no easy task, if you have only this graph to go by. But there is another way to determine the total energy burned by your household in a day, or in a week, or most often, in a month. That is by means of the electric meter. It measures electrical energy in kilowatt hours. Every month, without fail, the power company sends its representative to read that meter. This person takes down the number of kilowatt hours displayed, subtracts the number from the previous month, and a few days later you get a bill. This meter automatically keeps track of total consumed energy, without anybody having to do sophisticated integral calculus to find the areas under irregular curves such as the graph of Fig. 27.

