Report Sheet Lab 4 Circuits

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Florida Agricultural and Mechanical University *

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2054

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Electrical Engineering

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Apr 3, 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 0.00 1 and 2 3.18 0.02 1, 2 and 3 4.76 0.04 1, 2, 3 and 4 6.34 0.05  What is the relationship between voltage and current? Use data from your graph to support your answer. Voltage and current have a direct relationship according to Ohm's Law: as voltage increases, current increases proportionally, as shown in the graph.  Determine the slope of the line and record it in Table 3. TABLE 3:Resistor Data Resistance (  ) Slope (V/I) Percent Difference 970 ohms 987ohms 2.9%  How does the value of the slope compare to the resistance you measured? Calculate the percent difference. The values are very similar.  Use the results of your experiment to verify Ohm's Law. Is observed that the value of the slope is equal to the resistance so ohms law can be verified.  How does adding more batteries affect the power dissipated through the resistor? Support your answer mathematically and record your answer in variable form.

As the applied voltage is increased by adding more batteries, the power dissipated increases more rapidly. (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 (  ) 0.18 6.5 470.6 0.16 6.8 473.4 0.14 7.1 452.2 0.12 8.7 370.3 0.10 10 320.4 0.08 11.6 278.5 0.06 14.8 218.5 TABLE 7: Resistance and Area Circuit Data Diameter (m) Area (m 2 ) Current (A) Resistance (  ) 0.106 8.82 7.00 1004.2 0.106 8.82 7.72 906.85 0.106 8.82 8.60 814.15 0.106 8.82 9.45 741.00 0.106 8.82 10.22 685.80 0.106 8.82 11.10 631.50 0.106 8.82 12.00 582.72 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? Resistance increases with length in a direct proportion, assuming constant resistivity and cross-sectional area. 5. What is the relationship between resistance and area? Resistance decreases as cross-sectional area increases, with constant resistivity and length. 6. Determine the resistivity of the Play-Doh® from the slope of the graph. Since R varies directly with L, we anticipate observing a linear graph. Slope: 2282 2282*8.8e-5= 0.200 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. 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0 50 100 150 200 250 300 350 400 450 500 f(x) = 2281.96 x + 95.29 Resistance Vs. Lenght Lenght (m) Resistance (ohms)

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The percentage difference is very small, ,ess than one percent, this suggest that is not related to the changes in length. Resistivity remains an intrinsic characteristic of the material and remains constant regardless of physical parameters like length and area. 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 0.09