Lab 1.docx

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Texas A&M University *

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214

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Electrical Engineering

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Jan 9, 2024

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ECEN 214 - Lab Report Lab Number: 1 Lab Title: Introduction to Electric Circuits and Measurements Section Number: 517

Purpose: The main objective of this lab was to be able to change a fixed DC voltage source into a variable DC voltage source through the use of a voltage divider circuit. The varying voltage will be seen as the one or both of the resistor values are changed throughout the lab. We will be doing three different things to see how the voltage value can vary based on the resistor. We will see what happens when the first resistor is fixed and the second one is varied and vice versa. We will also see what happens when both resistor values are varying. We will also see how much the load resistance will affect the output voltage in the end. Procedure: For this lab, the needed equipment are a 9V battery or dc source, a 10k potentiometer, and different resistors. The first part of the experiment is to measure the voltage using the multimeter and then placing different load resistances onto the breadboard and recording the voltage for each resistor. Figure 1 displays what this part of the lab is supposed to look like. Figure 1: Load Resistance For the next part, a voltage divider circuit is created with the first resistor being the variable resistor and the second one being a fixed resistor. The largest and smallest voltage is then measured. Figure 2 is what the circuit is supposed to be. The next step is to add the load resistance to the voltage divider circuit and measure the voltage across the circuit's output terminals. Figure 3 represents this part of the lab.

Figure 2: Voltage divider Figure 3: Voltage divider with load resistance The same process is repeated however, the first resistor is the fixed resistance and the second resistor is the variable resistance. Make sure to record the voltages of the voltage divider output terminal. The last part of this lab is having both the resistors be variable resistance and measuring that voltage. Make sure to also add the load resistance and measure the voltage as done before in the last two parts. Data Tables and Plots: Task 1: Fixed DC Voltage Source Measurement For this task, different resistor values were placed across the voltage terminal to see how the voltage values would change as we would increase the resistor value. Voltage: 8.998 V Resistance (ohms) Voltage (V) 100 8.876 1,000 8.98 10,000 8.998 100,000 8.998 Task 2: Variable DC Voltage Source Measurement The first part of this task was to make R1 the variable resistor and R2 the fixed resistor. The next step was to add a load resistor to the circuit to see how the load resistance would affect the

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voltage values. As the load resistance value increased, it resulted in an increase in voltage as well. Voltage: 1.578 ≤ V ≤ 8.997 Voltage = 5.12V Resistance (ohms) Voltage (V) 100 0.5 1,000 2.586 10,000 4.257 100,000 4.566 Voltage = 1.49 V Resistance (ohms) Voltage (V) 100 0.134 1,000 0.740 10,000 1.360 100,000 1.480

B. R1 is fixed and R2 is variable Voltage: 0.037*10^-3 ≤ V ≤ 4.812 Voltage = 1.55 V Resistance (ohms) Voltage (V) 100 0.103 1,000 0.647 10,000 1.364 100,000 1.501 Voltage = 4.81 V Resistance (ohms) Voltage (V) 100 0.108 1,000 0.901

10,000 3.35 100,000 4.58 C. R1 and R2 variable Voltage: 0.003 ≤ V ≤ 8.99 Voltage = 1.452 V Resistance (ohms) Voltage (V) 100 0.107 1,000 0.647 10,000 1.292 100,000 1.434

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Voltage = 4.937 V Resistance (ohms) Voltage (V) 100 0.207 1,000 1.509 10,000 4.025 100,00 0 4.827 Discussion: For all three circuit configurations, in regards to being within 10% of the desired 5V, only the 100k ohm load resistor falls within. For the first two configurations where only one of the resistors vary, the 10k ohm and 100k ohm load resistor fall within the desired voltage range for 1.5V. However, in the last configuration where both resistors vary, only the 100k ohm load resistor falls within the desired 1.5V. It would be better to use a larger ohm resistor in the voltage divider if we wanted our circuit to be less sensitive. This is because the load resistance is in parallel with the resistor two. Thus, by having a larger ohm resistance, the resistor becomes more negligible leading to a smaller voltage drop. This is supported by how most circuit configurations can tolerate the higher ohm load resistors (10k and 100k ohm) while still producing the desired voltage. If you were to use a smaller ohm resistor, the circuit would become more sensitive and lead to a higher voltage drop. In order to see more power delivered to the load, it is better to use a larger ohm resistor value as the voltage drop would be significantly less than a smaller ohm resistor. Thus, more power would be delivered to the load.

Conclusion: In this lab, we learned how to transform a fixed DC voltage source into a variable DC voltage source by varying the values of two resistors. We saw how the value of the voltage would vary based on not only the value of the resistor but also its position in the circuit. To vary the values of the resistors, we replaced one of the resistors with a potentiometer. This lab helped show how the voltage across the voltage divider output terminals changes as we increase the resistance load. Signatures: