Name: Date: PC1222 Fundamentals of Physics II Basic Circuits 5 Laboratory Worksheet Part A: Ohm s Law and Resistances Resistance Colour Codes 1st 2nd 3rd 4th Resistance R (Ω) Current I (A) Voltage V (V) Data Table 1 Analysis A-1: For each resistor, determine the coded value of the resistance. Compare the coded value of the resistance with the measured value using percentage discrepancy. How does the percentage discrepancy compare to the codded tolerance of the resistor? Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Page 1 of 5
Basic Circuits Laboratory Worksheet Page 2 of 5 Analysis A-2: Perform a linear least squares fit to your data with the current I as the vertical axis and 1/R as the horizontal axis. Plot a graph of the current I against 1/R. Also show on the graph the straight line that was obtained by the linear least squares fit to the data as well as the error-bar of your data. Be sure to attach a copy of the graph (with the spreadsheet) to your laboratory report. Gradient: ± (units) y-intercept: ± (units) Correlation coefficient: Analysis A-3: For each resistor, calculate the ratio of voltage/resistance ( V/R). Compare the values you calculate with the measured values of the current I using percentage discrepancy. Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Question A-1: What can you conclude about the mathematical relationship between current I and resistance R? State clearly the basis of your answer. Question A-2: Ohm s law states that current is given by the ratio of voltage/resistane. Does your data concur with this? State clearly the basis of your answer. Question A-3: What were possible sources of experimental uncertainty in this experiment? Would you expect each to make your results larger or to make them smaller?
Basic Circuits Laboratory Worksheet Page 3 of 5 Part B: Series Circuit R 1 = I 0 = V 1 = R 2 = I 1 = V 2 = R 3 = I 2 = V 3 = R 12 = I 3 = V 12 = R 23 = V 23 = R 123 = V 123 = Data Table 2: Data for series circuit with resistors #1, #2 and #3. Analysis B-1: Calculate theoretical equivalent resistances of the combinations R 12, R 23 and R 123. Compare the values you calculated with the measured values respectively by calculating their percentage discrepancies. Show your work. Theoretical R 12 = (units) % discrepancy = % Theoretical R 23 = (units) % discrepancy = % Theoretical R 123 = (units) % discrepancy = % Question B-2: In a series circuit, on the basis of the data you recorded in Data Table 2, what are the patterns for how voltages get distributed with unequal resistances? Is there any relationship between the size of the resistance and the size of the resulting voltage? Question B-3: On the basis of your recorded data in Data Table 2, what is the pattern for how current behaves in series circuits? At this point, you should be able to summarize the behaviour of all three quantities resistance, voltage and current in series circuits.
Basic Circuits Laboratory Worksheet Page 4 of 5 Part C: Parallel Circuit R a = I 0 = V a = R b = I a = V b = R c = I b = V c = R abc = I c = V abc = I 4 = Data Table 3: Data for parallel circuit with resistors a, b and c. Analysis C-1: Calculate theoretical equivalent resistance of the combination R abc. Compare the value you calculated with the measured value by calculating the percentage discrepancy. Show your work. Theoretical R abc = (units) % discrepancy = % Question C-1: In a parallel circuit, on the basis of the data you recorded in Data Table 3, what are the patterns for how voltages get distributed with unequal resistances? Is there any relationship between the size of the resistance and the size of the resulting voltage? Question C-2: On the basis of your recorded data in Data Table 3, what is the pattern for how current behaves in parallel circuits? At this point, you should be able to summarize the behaviour of all three quantities resistance, voltage and current in parallel circuits.
Basic Circuits Laboratory Worksheet Page 5 of 5 Part D: Combination Circuit R A = I 0 = V A = R B = I A = V B = R C = I B = V C = R BC = I C = V BC = R ABC = I 4 = V ABC = Data Table 4: Data for combination circuit with resistors A, B and C. Analysis D-1: Calculate theoretical equivalent resistances of the combinations R BC and R ABC. Compare the values you calculated with the measured values respectively by calculating their percentage discrepancies. Show your work. Theoretical R BC = (units) % discrepancy = % Theoretical R ABC = (units) % discrepancy = % Question D-1: Do your data recorded in Data Table 4 for the combination circuit follow the same rules as they did in your circuits which were purely series or parallel? If not, state the rules you see in operation. Explain. 6 Laboratory Report Submit a laboratory report by ONE week after your laboratory session. Important: Before leaving the laboratory, have a demonstrator initial on your data table(s)! Last updated: Sunday 17 th August, 2008 4:04pm (KHCM)