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# lab2 - Diana Wu 803576180 21 October 2008 Physics 4BL Sec 5...

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Diana Wu 803576180 21 October, 2008 Physics 4BL Sec 5 DC and AC Circuits II. Introduction The purpose of this lab is to examine the properties and behaviors of DC and AC circuits under given conditions. For DC circuits, we verify Ohm’s law, test out series and parallel combinations, and examine the variation of the resistance of a length of copper wire and that of a diode with temperature. For AC circuits, we combine series circuits with reactive components and with resistors and study the results and we analyze RC and RL circuits under transient conditions by changing the applied potential discontinuously. III. Experimental Results DC Circuits 1. Verification of Ohm’s Law In this section, I connected the function generator to the given circuit board to create a circuit with a known resistor r and an unknown resistor R connected in series. Using Labview, I measured the voltage drop across r and gained data points to come up with an experimental value for R . Current vs. Voltage y = 0.0022x - 1E-06 -2.00E-02 -1.50E-02 -1.00E-02 -5.00E-03 0.00E+00 5.00E-03 1.00E-02 1.50E-02 2.00E-02 -8.00E+0 0 -6.00E+0 0 -4.00E+0 0 -2.00E+0 0 0.00E+00 2.00E+00 4.00E+00 6.00E+00 8.00E+00 Voltage (V) Current (A) Since current is constant through resistors in series, I know that calculating the current through the known resistor will give me the current through the unknown resistor. Thus when I graph the current through r versus the voltage across R , I expect a linear plot

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Current vs. Voltage -0.005 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 -12 -10 -8 -6 -4 -2 0 2 Voltage (V) Current (A) After Liquid N At Room Temp due to the relationship V = IR, where voltage is directly proportional to current. By obtaining the expected linear plot, I confirmed Ohm’s Law as well as obtained a value for the slope, or conductance (1/R), which is 0.0022 ohms -1 . Taking the inverse of this value will give me the experimental value for the unknown resistor. 2. Resistors in Series and Parallel For this section, I used a digital multimeter to measure the resistance across each of three different resistors, two of which were in series and two of which were in parallel. I then measured the resistance across the resistors in series and then across the resistors in parallel. By doing this I can compare my calculated values for the total
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lab2 - Diana Wu 803576180 21 October 2008 Physics 4BL Sec 5...

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