Ohms law abstract

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George Mason University *

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246

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Electrical Engineering

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Apr 3, 2024

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A-1 ABSTRACT Title: Ohm’s Law Date: 02/24/2024 Author: Mariam Sabah Lab partners: Sahar Pirzai, Sarai Rodriguez Class, Section & Lab group: PHY 246-2D2 This lab explored the essence of Ohm’s law and its significance in physics laboratory. The lab specifically focused on understanding how voltage, current and resistance in an active circuit are related. An active circuit has a power supply that connects to resistors or other circuit elements. Ohm’s law is used to predict circuit parameters and the equation is V=IR. The lab consists of four activities in which Voltage, resistance and currents will be measured to verify the initial predicted results. In activity 1, the main task was to rebuild the circuit given in figure 2. A resistor at 120 ohms was used as a constant while the voltages changed. The voltage was increased by 1.00 and the relationship between voltages and resistors were measured. The results were recorded until Voltage 10V. The measurements were put into an excel sheet and turned into a scatterplot graph. The graph agreed with Ohm’s law as it showed the current increasing with the voltage. The current thoroughly increased by 0.01 with every increasing voltage. The significance of the value was very close to the measured value with an error of less than 1%. In activity 2, the circuit was wired up to look like the circuit in figure 3 of the procedure. Two resistors were used, one valued at 10 Ω and one at 100 Ω. A battery and ammeter were also added to the circuit. The voltage across each resistor and the current were both predicted. The voltage of 5 had a current of 0.05 while the voltage of 30 had a current of 0.27 for R1. In R2, the voltage of 5 had a current of 0.03 while the voltage of 30 had a current of 0.15 for R2. When the resistor was changed to a paper clip, the voltage had increased because the paperclip is more resistant than the resistor. The dollar notes current became nonexistent when replaced because voltage and current do not flow through paper. In activity 3, two resistors of 100Ω each were used to design and build a parallel circuit. The current was measured through each resistor and then a third resistor valued at 10Ω was added. A hypothesis was then created for this activity. If all the resistors in parallel have the same resistance, then the current will remain the same. This hypothesis can be tested by constructing a circuit with two of the resistors in parallel and ammeter by each of the resistors and by the end near the battery. Therefore, when this was tested, the simulation illustrated that increasing the resistance of any resistor in the parallel circuit, it only changed the current of the resistor and decreased the final current. Adding a third resistor showed an increase in the current even though the resistance of the third resistor was larger than the sum of the first two. Therefore, the hypothesis was not supported. In activity 4, the following resistors were used, R1 =10 Ω, R2 = 22 Ω, R3 = 100 Ω, R4 = 220 Ω, R5 = 220 Ω. The power supply was attached to supply positions A and B on the circuit like in figure 4 of the procedure. The voltmeter was used to measure the voltage across each of the resistors. From the last lab results, the total resistance was 134.24 ohms. The total resistance for today's lab is 142.85 ohms. This was a 6.4% difference. The predicted values therefore do fall within the 5-10% interval as they are relatively close to one another and under 10% error. In like all experiments, errors happen. in activity 2, it states that resistors normally have a 5% tolerance. What this meant is that there is a 5% error rate present and whether the value of the resistance falls within that range that would need to be considered. Another example can come.

A-2 from activity 1 from the calculation of percent error. According to the value attained there is a 1.683% error which is significantly low (under 5%). Although error is present it is significantly low meaning that the measured value for R1 is close to the accurate and appropriate value attained from the activity. Furthermore, for activity 4, the calculation for the percent difference fell under the range of 10% but still has an error. Overall, the experiment was successful as we were able to find an answer to our hypothesis and achieve the main goals of the procedure.

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