lab 5

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Temple University *

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1062

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Electrical Engineering

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Feb 20, 2024

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docx

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Melissa Haddadi Lab5: Series and Parallel Circuits with Resistivity Introduction: The purpose of this experiment is to study the difference between electrical circuits connected in series and parallel and how the voltage changes. We used light bulbs and wires to see the changes we also used Ohm’s law which is V=IR. In a series connection same current “ I ” flows, voltage has to split. while in a parallel the voltage drop remains the same. series, Req=R1+R2+…+RN parallel, 1/Req = 1 /R1 + 1 /R2 +…+ 1/ RN Procedure: Part I. We had to Hook up the complete circuit with one bulb with the Insertion of the batteries as a voltage source to the circuit, we noted the brightness of the single bulb. We made a prediction that placed a second bulb in series with the first the brightness would be dimmer then we confirmed it by setting it up. we then added our second bulb in parallel then brightness stayed unchanged for this step. Sources of Error: we were measuring the brightness of lightbulbs using naked eyes which could be misleading and not accurate. possible inaccuracy of multimeter data values. For the most part, we took precautions in making sure that all the connections were made correctly, all the probes are properly placed on all the terminals.

Questions: Question 1. Explain your results for both the series and parallel circuits based on Ohm’s Law. Our results follow Ohm’s which states that I=V/R because the light bulb gets dimmer after the addition of the other bulb to the circuit. due to the increase in resistance, which caused a decrease in the current flowing through the bulbs. a) If we remove one bulb from the series circuit, what do you think would happen to the other bulb? If we remove one from the parallel circuit? Test this and record the results. Briefly, explain your observations from the two cases. If one bulb is removed from a series circuit,) the other bulb will not work. If one bulb is removed on the parallel circuit the other light bulb will still work Question 2. Use your findings to explain why strings of lights such as Christmas lights are more reliable when the lights are all strung together in parallel. Strings of lights such as Christmas lights are more reliable when the lights are all strung together in parallel because if one bulb goes out, the others will still work since they are still receiving a current they will also be equally bright. . Question 3. Use Ohm’s law to explain why having too many parallel resistors can cause a high current to flow out of the power supply (this is why circuit breakers trip when you plug in too many appliances on a single circuit in your house). Req=R/n ..1 n is the number of the resistance. I=V/Req I=n(V/R). 2 When the number of the resistance (n) goes up in the circuit the current will increase. Question 4. Do the voltages V ab and V bc corroborate your observations of the brightness? Explain.

Yes, the voltages Vab and Vbc corroborate our observations of the brightness because we observed that the light in series for the one resistor was bright. Then for the other two resistors in parallel, the light was dimmer Question 5. Meter’s resistance = 1000R Current in bulb = I1 = V / R Current in meter = I2 = V / 1000R I1 / I2 = 1000 the current flowing through the meter (I2) is 1000 times less than the current flowing through the bulb (I1), the multimeter does not affect the circuit. Question 6. Is the relationship of resistance vs length linear? Does the best-fit line pass through the origin? What does this tell you about the relationship between R and length l? Yes, the relationship of resistance vs length is linear. The best fit line does not pass exactly through the origin. the relationship between resistance and length is directly proportional. Question 7. Which of the three graphs shows the best linear relationship? What does this tell you about how R is related to the wire cross-section area? the graph of resistance vs diameter shows the best linear relationship the resistance is directly proportional to the wire cross-section area, so as one changes the other changes at a constant rate. Discussion: This experiment was successful. We developed skills in building series and parallel circuits, differences were examined using Ohm’s Law: Circuit in series has higher resistance but the same current flowing through each of their component; on the other hand, Circuit in parallel, have lower resistance but the same voltage. we were able to predict how the light bulbs would change in brightness. Light bulbs in a series are dimmer compared to a single light bulb because the brightness is being shared between the two bulbs. However, those that are in parallel have the same brightness because the two light bulbs are independent of each other.

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