Report Sheet Lab 4 Circuits - Answers - Jamie Assaf

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Kennesaw State University *

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2212

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Electrical Engineering

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Jan 9, 2024

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Report Sheet CIRCUITS (LAB 4) (Part 1-OHMS’S LAW)  Plot a graph of Table 2. Construct your plot on a computer program such as Microsoft Excel®. If you do not have a graphing program installed on your computer, you can access one on the internet via the following links: http://nces.ed.gov/nceskids/createagraph/ http://www.onlinecharttool.com/graph?selected_graph=bar . TABLE 2: Voltage Readings of Different Battery Combinations Battery Combination Voltage Current 1 1.58 1.4*10^-3 1 and 2 3.09 3*10^-3 1, 2 and 3 4.63 4.45*10^-3 1, 2, 3 and 4 6.21 6*10^-3  What is the relationship between voltage and current? Use data from your graph to support your answer. Voltage and current are directly proportional to each other as the graph is a straight line  Determine the slope of the line and record it in Table 3. TABLE 3:Resistor Data Resistance (  ) Slope (V/I) Percent Difference 10.3 9.4375 8.37  How does the value of the slope compare to the resistance you measured? Calculate the percent difference. The slope and the measured resistance are not exactly some there is some error. The percentage difference is 8.37%  Use the results of your experiment to verify Ohm's Law. Since we get a straight line from the graph, I & V which is ohm’s law.  I=V/R, here R is the constant proportionality known as resistance.  How does adding more batteries affect the power dissipated through the resistor? Support your answer mathematically and record your answer in variable form.

(Parts 2 and 3 HOW AREA AND LENGTH AFFECT RESISTANCE) 1. Calculate the area for each diameter tested. Record area values in Table 7. 2. Find the resistance in each case of the Play-Doh® using Ohm’s Law, and finish completing Tables 5 and 7. TABLE 5: Length and Resistance Circuit Data Length (m) Current (A) Resistance (  ) 0.184 6.58*10^-3 470.88 0.16 6.82*10^-3 473.61 0.19 7.14*10^-3 452.38 0.12 8.71*10^-3 370.84 0.1 10.08*10^-3 320.44 0.08 11.6*10^-3 278.45 0.06 14.78*10^-3 218.54 TABLE 7: Resistance and Area Circuit Data Diameter (m) Area (m 2 ) Current (A) Resistance (  ) 0.0106 8.82*10^5 6.98*10^-3 1004.3 0.0196 8.82*10^5 7.73*10^-3 906.86 0.0106 8.82*10^5 8.61*10^-3 814.17 0.0106 8.82*10^5 9.46*10^-3 741.01 0.0106 8.82*10^5 10.22*10^-3 685.91 0.0106 8.82*10^5 11.1*10^-3 631.53 0.0106 8.82*10^5 12.03*10^-3 582.71 3. Create plots of Resistance vs. Length and Resistance vs. Area. Construct your plot on a computer program such as Microsoft Excel®. If you do not have a graphing program installed on your computer, you can access one on the internet via the following links: http://nces.ed.gov/nceskids/createagraph/ or http://www.onlinecharttool.com/graph? selected_graph=bar. 4. What is the relationship between resistance and length? R = PL/A R∞L Meaning that the resistance is proportional to the length.

5. What is the relationship between resistance and area? R = PL/A R∞1/A Meaning that resistance is inversely proportional to the area. 6. Determine the resistivity of the Play-Doh® from the slope of the graph. Resistivity = m * Area = 2223 * 8.82 * 10^-5 = 0.20 7. Does the resistivity of Play-Doh® change when the length or area changes? Explain your reasoning. Hint: A percent difference calculation will be helpful. R = ρ * L/A ρ = R * A/L A = 8.82*10^-5 8. Calculate the current density, J, for all Play-Doh® radii in Table 6. What trend do you observe? TABLE 6: Cylinder Circuit Area Circuit Data Battery Voltage (V) Cylinder Length (m) 3.16 0.090

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