EM4_Manual

EM4_Manual - General Physics II Lab EM4 DC Circuits General...

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General Physics II Lab EM4 DC Circuits General Physics II Lab EM4 DC Circuits Purpose In this experiment, you will learn applications of Ohm’s law and Kirchhoff’s rules in various DC circuits. Equipment and components Resistors, breadboard, multimeter, and AA sized batteries with holder. Background Ohm's Law describes the relationship between current I , voltage V , and resistance R in simple DC circuits. For series circuits, such as that shown in Fig. 1, the devices (resistors) are connected in such a way that there is a common current I flowing through each of the devices. In this case, we have I = I 1 = I 2 = I 3 and the total resistance of the circuit is given by: R Total = R 1 + R 2 + R 3 ( 1 ) Figure 1 Resistors in series Figure 2 Resistors in parallel For parallel circuits, such as that shown in Fig. 2, the devices (resistors) are connected in such a way that a common voltage is supplied across each of the devices. In this case, we have V = V 1 = V 2 = V 3 and the total resistance of the circuit is given by: R Total = 1 / (1/R 1 + 1/R 2 + . . . 1/R n ) (2) In many practical applications, the DC circuits used are more complex; they may have a number of power sources and branches, making the use of Ohm's Law impractical or impossible. In 1857 a German physicist, Gustav Kirchhoff, developed two rules to solve the current, voltage and resistance in complex circuits. Kirchhoff's Current (Junction) Rule : The sum of the currents entering any junction (or node) in a circuit must equal the sum of the currents leaving that junction. Put in another way, no matter how many paths into and out of a single junction (or node), all the currents leaving the junction must equal the sum of the currents entering that junction. Kirchhoff's Voltage (Loop) Rule : The algebraic sum of the voltages across all elements around any closed circuit loop must be zero. Put in another way: the voltage drops across all the elements around any closed loop must equal the applied voltages. Revised: 13 November 2009 1/12
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General Physics II Lab EM4 DC Circuits Procedure I. Resistance and voltage in different circuits 1. Choose three resistors of different values. Record the colour code of each resistor (see Appendix 1 for more details) in Table 1. Mark them as #1, #2 and #3. 2. Find the coded resistance value and tolerance value (refer to Appendix 1) of these resistors. Record them in Table 1. 3. Use the multimeter to measure the actual resistance of each resistor (refer to Appendix 2). Record your results in Table 1. 4.
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EM4_Manual - General Physics II Lab EM4 DC Circuits General...

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