Physic lab 4 2024

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Feb 20, 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 1.72 0.0017 1 and 2 3.25 0.0031 1, 2 and 3 4.83 0.0047 1, 2, 3 and 4 6.51 0.0063  What is the relationship between voltage and current? Use data from your graph to support your answer. According to Owens law voltage is directly proportional to current because the potential difference between the ends of resistance increases the current  Determine the slope of the line and record it in Table 3. TABLE 3:Resistor Data

Resistance (  ) Slope (V/I) Percent Difference 1038 1035.3 2.9%  How does the value of the slope compare to the resistance you measured? Calculate the percent difference.  Use the results of your experiment to verify Ohm's Law. You can verify that Ohm's Law works by easily using the equation V=IR, where V=voltage, I=current, and R=resistance. For example, 1.72=(0.0017 × 1011.8)  How does adding more batteries affect the power dissipated through the resistor? Support your answer mathematically and record your answer in variable form. Power dissipated across resister=V^2/R, so if batteries are added, V will increase, and so power dissipated will also increase. Power dissipated across resistor is directly proportional to number of batteries added in series with resistor. (Parts 2 and 3 HOW AREA AND LENGTH AFFECT RESISTANCE) 1. Calculate the area for each diameter tested. Record area values in Table 7. V=3.25v 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 (  ) 0.20 8.87*10^-3 366.4 0.18 7.83*10^-3 415.1 0.16 6.20*10^-3 524.2 0.14 5.37*10^-3 605.2 0.12 4.61*10^-3 705 0.10 3.88*10^-3 837.6 0.08 3.21*10^-3 1,012.5 TABLE 7: Resistance and Area Circuit Data Diameter (m) Area (m 2 ) Current (A) Resistance (  ) 0.0107 8.83*10^5 6.99*10^-3 1004.3

0.0197 8.83*10^5 7.74*10^-3 906.98 0.0107 8.83*10^5 8.62*10^-3 814.39 0.0107 8.83*10^5 9.47*10^-3 741.29 0.0107 8.83*10^5 10.23*10^-3 686.22 0.0107 8.83*10^5 11.11*10^-3 631.86 0.0107 8.83*10^5 12.04*10^-3 583.06 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? sorely rootereste len = PA, RaL, which means resistance 5. What is the relationship between resistance and area? The expression of the resistance is R = V/I = pL/A, R a 1/A, which means resistance is inversely proportional to the area. 6. Determine the resistivity of the Play-Doh® from the slope of the graph. The slope represents resistivity, or opposition to a flow of charge of the Play-Doh®. The Sesistance Increases. As0, The thiner Phe Play Doe, Ihe gieater the es sant 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. Yes, the resistivity changes changing from length to area.

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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) 1. According to Ohm’s Law, what happens to the voltage and current of a resistor as the resistance increases in the circuit shown in Figure 1? When resistance is increased then the value of voltage and current across the resistor decrease

2. If a 100 Ω resistor is attached to a 5 V battery, how much current flows through the resistor? 50mA 3. If a wire’s length is cut in half, by what factor does the wire’s resistance change? 1/2 4. If a wire’s area is reduced by half, by what factor does the wire’s resistance change? Double 5. If the diameter and length of a wire are both decreased by half, how does this affect the resistivity of the wire, ρ?

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