Physics 224 Lab 4 Resistor Circuits

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California Baptist University *

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PHY224

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Electrical Engineering

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Apr 3, 2024

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Christina Villanueva Raquel Ibarra Section D 2/7/24 Physics 224L Lab #4: Resistor Circuits Purpose: The purpose of Lab #4 Resistor Circuits is to provide us with hands-on experience in analyzing resistor circuits and measuring voltage and electric current flowing through various circuit elements. The lab applies fundamental principles such as Ohm's Law, Kirchhoff's junction law, and Kirchhoff's loop law to understand and analyze circuit behavior. Through practical experimentation with different circuit configurations, including series and parallel arrangements of resistors, students are tasked with measuring currents and voltages across components and verifying theoretical expectations. The lab aims to reinforce key concepts in electrical circuit analysis and enhance our understanding of how resistors behave in different circuit configurations. Part 1: Circuit #1 Create the circuit shown below. Measure the current I and voltage V across each resistor and the battery. Mark the measured values on the circuit diagram below where you measured them. 100= 1.172 V; 0.01172 amps 200=2.56 V; 0.0128 amps 100 W 220 W 5V =4.92 V 100 W

100=1.167 V; 0.01167 amps Question #1: Compare the currents flowing through each resistor? Is this consistent with Kirchhoff’s junction law? Explain. The currents flowing through each resistor are relatively 0.0100 amps. When the voltage is applied through a resistor, the electrons flow through it creating a current. This current flow is determined through Ohm’s Law stating that current flow through resistor is equal to the voltage applied divided by the resistance. I=V/R. With Kirchhoff’s Junction Law, at any junction in an electrical circuit, the sum of currents entering the junctions must be equal to the sum of currents leaving the junction. With current flow through resistors, the law holds true as the current entering a resistor is equal to the current leaving the resistor. These values are relatively close and consistent, indicating that the current flowing into the junction equals the current flowing out. This consistency confirms Kirchhoff’s junction law, which is grounded in the principle of charge conservation. Question #2: Compare the voltage differences across the 100 ° and the 220 ° resistor. Which resistor has the largest voltage difference? Why? Is the measured voltage across each resistor what you expect from Ohm’s Law? Show your calculation. The voltage across the 100Ω resistor is measured as 1.172 V. The voltage across the 220Ω resistor is measured as 2.56 V. From these measurements, we can see that the 220Ω resistor has the largest voltage difference. The reason for this lies in the fundamental principles of series circuits. In a series configuration, the same current flows through each resistor, but the voltage drop across each resistor is proportional to its resistance. Therefore, the resistor with the higher resistance will have a larger voltage drop across it. To verify whether the measured voltages across each resistor align with Ohm’s Law, we can use the formula V = IR, where V is the voltage, I is the current, and R is the resistance. Since the current flowing through each resistor is the same in a series circuit, we can use the measured current value for our calculations. Let's calculate the expected voltage across each resistor: For the 100Ω resistor: V = IR = (0.01172 A)(100Ω) ≈ 1.172 V For the 220Ω resistor: V = IR = (0.01172 A)(220Ω) ≈ 2.5784 V Comparing the calculated values with the measured values, we can see that they are very close. Any discrepancies between the calculated and measured values could be due to experimental errors or slight variations in the circuit components. Overall, the measured voltages across each resistor in Circuit #1 are consistent with Ohm’s Law.

Question #3: What is the total voltage differences across all three resistors? Is this what you expected from Kirchhoff’s loop law? Explain. Voltage across the 100Ω resistor = 1.172 V Voltage across the 200Ω resistor = 2.56 V Voltage across the second 100Ω resistor = 1.167 V Total voltage difference = Voltage across the 100Ω resistor + Voltage across the 200Ω resistor + Voltage across the second 100Ω resistor = 1.172 V + 2.56 V + 1.167 V ≈ 4.899 V According to Kirchhoff's loop law, in a closed loop in a circuit, the sum of the voltage drops should equal the total voltage supplied by the battery. In this case, the total voltage difference across all three resistors is approximately 4.899 V, which is very close to the voltage supplied by the battery, assuming it is 5 V. This observation aligns with Kirchhoff's loop law, confirming that the sum of the voltage drops across all components in a closed loop equals the total voltage supplied by the battery. Therefore, the total voltage difference across all three resistors in Circuit #1 is consistent with Kirchhoff's loop law. Question #4: Can you generalize the above observations about voltage differences for resistors in series? In series circuits, voltage differences across resistors are proportional to their respective resistances. The total voltage supplied by the source equals the sum of individual voltage drops across each resistor. Higher resistance leads to a more significant voltage drop. Therefore, in series configurations, voltage differences across resistors depend on their resistance values and add up to the total voltage provided by the source. This principle holds regardless of the number of resistors in the series arrangement. Question #5: What is the equivalent resistance of circuit #1? Show your calculation. The equivalent resistance (Req) is calculated as follows: Req = R1 + R2 + R3 = 100Ω + 200Ω + 100Ω = 400Ω Therefore, the equivalent resistance of Circuit #1 is 400Ω. Part 2: Circuit #2 Create the circuit shown below. Measure the current I and voltage V across each resistor and the battery. Mark the measured values on the circuit diagram below where you measured them.

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