KIRCHOFFS-RULES - update

2 the voltage of the mictitious perfect battery

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Unformatted text preview: ed in PART I using Kirchoff's Laws. In Part II, you will use the loop rule to calculate the internal resistance of a battery. The current that any real battery can produce is limited. While the electrochemical factors that limit the current are complex, any real battery behaves as if it were a perfect battery connected in series with an internal resistance ( in Fig. 2). The voltage of the Mictitious perfect battery is assumed to be the same as the open- circuit voltage of the real battery. The drop in the terminal voltage of the real battery, , that occurs when a current is drawn from the battery is treated as being the voltage drop across that internal resistance1 . The smaller the internal resistance is, the more current the battery can deliver. One could Mind the internal resistance by measuring the current Mlowing through a dead short across the terminals and calculate from Ohm's Law, but this method is not recommended. Only a small current should be drawn from the battery when measuring . However, if only a small current is drawn from the battery, the change in the terminal voltage of the battery will be too small to measure with a conventional needle- type voltmeter. However, the digital meter, with its four- digit accuracy, can easily measure the change. Figure 1 A battery is treated as an ideal source of emf, , in series with an internal resistance, . The battery terminal voltage is . 5. Equipment Required • • • • Set of resistors Banana plug cables Power Supply Digital Multimeter (DMM) 6. Experimental Procedure 6.1. Part #1: Currents and Voltage Through Simple Circuits...
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This note was uploaded on 05/15/2013 for the course PHY 2170 taught by Professor Blank during the Fall '08 term at Wayne State University.

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