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Florida Atlantic University *

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PHY2049L

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Electrical Engineering

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Feb 20, 2024

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Experiment 2: Resistors in Series and Parallel Connections (1) Student name: Caden Huffman Pre-lab section: 1) Introduction: Explain the theory behind this experiment in a paragraph between 150 and 250 words . (1.5 points) In this experiment, I will explore the relationships between voltage, current, and resistance in electrical circuits. This concept is defined within Ohms law, Ohms law explains that when we apply voltage across a conductor, resulting current from it is directly proportional to that voltage, the expression for this is R=V/I, as R=resistance V=Voltage and I=Current. When resistors are connected in a series, they are lined up one after the other. The total resistance of this system can be calculated by the sums of each individual resistor. However, when resistors are connected in parallel with each other, they are attached side by side with each other. The equivalent resistance is calculated by the formula 1/R p =1/R 1 +1/R 2 . Unlike a series connection, a parallel connection the voltage across each resistor remains the same. So, the idea of this experiment is to understand how resistors behave when they are connected in different configurations, and how it affects the current and voltage in said circuit. Suppose you are using external resources; include the reference. It would be best if you had any relevant formulas and explanations of each term. You may use the rich formula tools embedded here. 2) Hypothesis: In an If /Then statement, highlight the purpose of the experiment . (0.5 points) If a lightbulb that is connected to the supplied voltage becomes disconnected, then the rest of the system fails, as the voltage has no starting point to flow through and the rest of the system is not connected with the supplied voltage. For instance: If two same shape objects with different masses are dropped from the same height, they will hit the ground simultaneously. Post-lab section: 3) Discussion: In a paragraph between 100 and 150 words , explain what you learned from the results obtained in the experiment. What conclusion can you draw from the results of this lab assignment? (2.0 points) In completing this experiment I learned the differences between series, parallel, and complex circuits. Not only did I learn about this differences but I experienced them which gave further insight into the topic being explored. I learned that it would be unwise to connect the lights in a home in a series or

complex connection as certain lights would rely on another because of the branches of connections these series have. I also learned that current flows differently through out each different system and is responsible for the power of the light bulb if the resistance remains constant. Which was the reason why some light bulbs shined brighter than others in the system. In further detail I learned that the way certain cricuits branch can affect the current that flows through the system and it reaching its certain connections. What results did you obtain? Compare them to each other, discuss what they tell us about the experiment. Compare the measured/experimental results to the theoretical expectations using the percent error, discuss what they tell us about the experiment. How do these results confirm the theory? What do these results imply in terms of our expectations? If results are far off, discuss possible sources of error (besides human error), what do the percent error tells us? 4) Conclusion: In one sentence, compare the results of the experiment with your Hypothesis. Why? (1 point) Explain why the results you obtained either prove or disprove your hypothesis statement The results of the experiment proved my hypothesis correct, as removing light bulb #1 in the experiment, stopped the connection of the voltage to the other light bulbs which in return they did not light up because there was no current flowing through them. 5) Data Analysis: Attach an image of the lab manual pages containing tables with final calculated values, figures, plots, charts and responses to questions here. (11.5 points) This should include: Table 1: Data and Analysis: 1.5 points, Q a: 0.25 points, Q b: 0.25 points, Q c: 0.25 points, Q d: 0.25points Table 1 DMM readings and observed bulbs’ brightness for the circuits in Fig. 4 (in the lab manual). Source Voltage V S Cases DMM reading (mA) Current through power supply (mA) Current through each bulb (mA) Observed brightness 5V Fig. 4(a) 220.6mA 220.6mA 220.6mA Bright Fig. 4(b) 145.37mA 145.37mA 145.37mA Dim Fig. 4(c) 115.28mA 115.28mA 115.28mA Really Dim Fig. 4(d) 97.85mA 97.85mA 97.85mA No brightness Fig. 4(d) but with one light bulb removed 0 0 0 N/A Data analysis and questions for Measurement #1: (a) Put the required current values in the columns #4 and #5 (from the left) of Table 1. Completed

(b) Is the current through the power supply and each bulb (in Table 1) increasing or decreasing with increasing the number of bulbs from Fig. 4 (a) to Fig. 4 (d)? Why? If the # of light bulbs increases then the resistance of the circuit increases, if the light bulbs are connected in a series. This means while resistance increases the current decreases. (c) Is there any correlation between the current through each bulb and the observed bulbs’ brightness listed in Table 1? If yes, is the correlation consistent with P IV = = I R 2 ? The brightness of the light bulb is proportional to the power of the light bulb, so if the current increases which is I in the equation then the light bulb will get brighter. (d) Are the lights at your home connected in series? Why? In my home, the lights are connected by a parallel connection, because in a parallel connection, the same voltage is distributed throughout all lights so if one fails the other ones do not go out unlike in a series. Table 2: Data and Analysis: 1.5 points, Q 1: 0.25+0.25 points, Q 2: 0.25 points, Q 3: 0.25 points Q 4: 0.25 points, Q5: 0.25 points Table 2 DMM reading and observed bulbs’ brightness for the circuits in Fig. 5. Source Voltage V S Cases DMM reading (mA) Current through power supply (mA) Current through each bulb (mA) Observed brightness 5V Fig. 5(a) 216.3mA 216.3mA 216.3mA Bright Fig. 5(b) 426.8mA 426.8mA 213.4mA Really Bright Fig. 5(c) 622.8mA 622.8mA 207.6mA Really Bright Fig. 5(d) 812.4mA 812.4mA 203.1mA Really Bright Fig. 5(d) but with one light bulb removed 598.7mA 598.7mA 199.6mA Less bright then previous measurements Data analysis and questions for Measurement #2: (a) Put the required current values in the columns #4 and #5 (from the left) of Table 2. Completed (b) Is the current through the power supply and each bulb (in Table 2) increasing or decreasing with increasing the number of bulbs from Fig. 5 (a) to Fig. 5 (d)? Why?

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If the number of light bulbs increases the current in each of them stays the same in this system of connections because the currents can be different in certain branches but they all add up to equal the same total amount of current in the system. (c) Is there any correlation between the current through each bulb and observed bulbs’ brightness? Why? The voltage across each light bulb in the system remains the same, which means that the brightness also stays the same, so there is no correlation between brightness and current. (d) Are the lights at your home connected in parallel? Why? My lights at home are connected in parallel because the same voltage is supplied across each light bulb in the parallel system across each bulb, so the brightness will be the same for all light bulbs. (e) The maximum output current from the DC power supply #1 is 2 A. What is the maximum number of light bulbs (used in this experiment) can be connected in parallel with the DC power supply #1? What will happen if more than 10 such light bulbs are connected in parallel with the DC power supply #1? As seen from the table that each lightbulb has a current of about .2A, and the total number of supplied Amperes is 2, then 2/.2=10 light bulbs. So if the connection has more than 10 light bulbs connected then the system will fail to supply each light bulb in the system with 0.2A. Table 3: 1.25 point, Data and Analysis: 1.5 points, Q 1: 0.25+0.25 points, Q 2) a, b: 0.25points, Q 3: 0.25 points Table 3 DMM reading and observed bulbs’ brightness for the circuits in Fig. 6. Source Voltage V S Cases DMM reading (mA) Observed bulbs’ brightness bulb #1 bulb #2 bulb #3 bulb #4 5V All 4 light bulbs are in circuit 134.3mA Dim Light No Light No Light Light 10V All 4 light bulbs are in circuit 197.29mA Bright Very Dim No Light Brightest Light bulb #1 is removed 0mA N/A No Light No Light No Light Light bulb #2 is removed 169.11mA Little Dim N/A Decently Bright Decently Bright Light bulb #3 is removed 168.22mA Little Dim Decently Bright N/A Decently Bright Light bulb #4 is removed 0mA No Light No Light No Light N/A NO DATA ANALYSIS FOR TABLE 3 Table 4: Data and Analysis: 2 points, Q 1: 0.25 points, Q 2(a): 0.25 points, Q 2(b): 0.25 points, Q 3: 0.25 points

Table 4. Table 4 Current through each light bulb in Fig. 6 Source Voltage V S Cases I 1 (mA) I 2 (mA) I 3 (mA) I 4 (mA) 5V All 4 light bulbs are in circuit 134.3mA 67.15mA 67.15mA 134.3mA 10V All 4 light bulbs are in circuit 197.29m A 98.65mA 98.65mA 197.29m A Light bulb #1 is removed 0mA 0mA 0mA 0mA Light bulb #2 is removed 169.11m A 0mA 169.11mA 169.11m A Light bulb #3 is removed 168.22m A 168.22m A 0mA 168.22mA Light bulb #4 is removed 0mA 0mA 0mA 0mA Questions on Measurement #3: 1. With all 4 bulbs are in circuit (Fig. 6), use the data in Table 4 explain why bulbs #2 and #3 are dimmer at V S = 5 V than at V S = 10 V. The bulbs with the voltage at 5V are dimmer then the bulbs with a voltage of 10V because the brightness of the bulb is given by its power and since the resistance of all the light bulbs are the same its brightness correlates with the current through the light bulb and since 5V is less then 10V the 10V light bulb is brighter. 2. Using the measured data of current in Table 3 and the data in Table 4 explain: (a) why bulbs #1 and #4 are brighter than bulbs #2 and #3 at both V S = 5 V and 10 V when all the 4 bulbs are in circuit; The bulbs #1 and #4 are brighter than bulbs #2 and #3 because the measured current in them are half as much as the current in the light bulbs at the end. This because the current flowing through the system is split between two branches which divides the current from the supplied voltage in half. (b) why bulbs #3 becomes as bright as bulb #1 and #4 after bulb #2 is removed (all other bulbs are remained in the circuit). Bulb #3 becomes as bright as bulbs #1 and #4 because when you take bulb #2 out of the system the current no longer is split between two different branches and instead only flows through one branch. So then it has the same measured current as bulb #1 and #4 and it is a bright as them. 3. Can the lights at your home be connected using the circuit in Fig. 6? Why?

The lights in my home cannot be connected using this circuit because each individual light in my home cannot be dependent on another light for brightness. In this system certain lights brightness depend on others and in some instances the whole entire system for lighting depends on a singular light being connected. 6) Calculations: Attach an image all your calculation pages here . (1 point) Table 2: Current through each bulb: 0.5 points, Table 4: I 1 , I 2 , I 3 , I 4 : 1 point Calculation pages must include the following: i. Label calculations for each table. ii. Write out formulas before plugging in measured values. iii. Values plugged into the formulas must contain units and proper number of significant figures (units must be written out throughout calculations). iv. Final calculated values recorded in tables and calculation pages must contain units and proper number of significant figures. All work for calculations must be shown to receive credit for data analysis.

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7) End of Experiment Questions: Attach an image of the lab manual pages containing your responses to the end of experiment questions here. (0.5 points) Question 1 : 0.5 point Lab reports must be written individually by each student from beginning to end. No credit will be given for copied work.