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Ohm's Law and Resistors in Series and in Parallel Presented by Mahmud AbdurRahman & Nazim Uddin Physics 2.3 honor Class DR. Roman Kezerashvili

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Objectives: Objectives: 1. Verify law by observing the dependence of the electric current as a function of voltage and as a function of resistance. 2. Determine the equivalent resistance of series and parallel combination of resistors and compare the results with the theoretical predictions. 3. Study currents flow and voltages in series and parallel circuits.

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Equipment 1R esistance box 2. Digital Multmeter 3. DC power supply with adjustable voltage (0-20 V) 4. Resistors board 5. Connecting wires 6. Switch

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Theory What is the Ohms Law Ohms law States that current through a resistor is directly proportional to the applied voltage V and inversely proportional to the resistance R of the resistanceOhms law States that current through a resistor is directly proportional to the applied voltage V and inversely proportional to the resistance R of the resistance Ohms law is not a fundamental law of natureOhms law is not a fundamental law of nature An empirical relationship that is valid for certain materialAn empirical relationship that is valid for certain material at constant temperatureat constant temperature Electric current I=Q/T Ohms Law I=V/R

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Procedure Part1Part1 1.Investigate the variation of the current with potential difference when the resistance is constant1.Investigate the variation of the current with potential difference when the resistance is constant 2. Investigate the variation of the current with resistance when the voltage is constant. Part II 1.Resistors in series 2. Resistors in Parallel

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Ohms Law( The relationship among current,voltage and resistance) Resistors in Series Resistors in Parallel Data: » Table 1. The Voltage Dependence of Current (Constant resistance) Power supply, VR 1 = 1000 R 2 = 1200 Voltage V, V Current I, A Voltage V,V 4 4.020.0040 4.020.0033 5 5.020.0049 5.020.0041 6 6.020.0060 6.030.0049 7 7.020.0070 7.040.0058 8 8.010.0079 8.010.0066 9 9.010.0090 9.000.0074 10 10.030.0099 10.020.0082

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Data Resistance R, 1/R, -1 Current I, A 700 0.00143 0.01700 800 0.001250.01490 900 0.001110.01320 1000 0.001000.01190 1100 0.000910.01084 200 0.000830.00994 Voltage Power supply V,V=12 V from Slope,V 11.874 %Difference 1.06%

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Continuation »Table 3. Resistors in Series I = 0.0024 A, V = 12 V, R = 4950 Voltage V, VResistorsCurrent I, AVoltage V, VResistance R, R A 0.00248.743620 R B 0.00242.631090 R C 0.00240.57230 Equivalent resistance from equation (9) R = 4940 ; % difference = 0.20% Total voltage from equation (5) V = 11.94 V; % difference = 0.50% –Table 4. Resistors in Parallel I = 0.032 A, V = 6 V, R = 185.6 Voltage V, VResistorsCurrent I, AVoltage V, VResistance R, R A 0.001863620 R B 0.005461090 R C 0.0266230

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GRAPH

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Graph 2

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Calculation and Analysis: 1.Use data from Table 1 and plot a graph of the current I us the voltage V for both values of the resistance. Determine the slope of the graph. From the slope of the graph find the resistance using » R=1/slope and compare it to the actual value of resistance by calculating a percent difference. – – 2.Use data from Table 2 and plot a graph of the current I versus the 1/R. Determine the slope of the graph. Compare the slope of the graph with the output voltage of power supply by computing a percent difference. – – 3.Resistors in series. – – Using the resistors value compute the equivalent resistance R of the circuit by using equation (9). Compare this value with your experimental measurement by finding a percent difference. – – Using the measured voltages compute the total voltage V by using equation (5). Compare this value with your experimental measurement by finding a percent difference.

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Continue Calculations

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According to the experiment we observed that the electric current through a resistor is directly proportional to the applied voltage and inversely proportional to the resistance of the resistor and verified Ohms law.According to the experiment we observed that the electric current through a resistor is directly proportional to the applied voltage and inversely proportional to the resistance of the resistor and verified Ohms law. We also observed the difference between series and parallel connections.We also observed the difference between series and parallel connections. I LOVE PHYSICS THANKS TO PROFESSOR DR. ROMAN FOR MAKING PHYSICS SO ENJOYABLE.

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