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Ohm's Law Physics Lab #20

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Introduction

Ohm's Law Physics Lab #20 Name: Diana Abou Hassan Partners: Sara Jaber Michael Muhanna Rami Jachi Date Performed: 14/11/2002 Date Due: 21/11/2002 Teacher: Mrs. Khoury Saab Objective: The objective of this lab is to determine the relationship between the potential difference across a conductor and the electric current through it. \ Materials: - Low voltage variable DC power supply\ - Two different resistors - 2 digital multimeters - connecting wires Procedure: Please refer to lab sheet. Data Collected: Resistor 2 Voltage (V) 1 1.5 2 2.5 3 3.5 Current (mA + 0.01mA) 0.42 0.72 1.16 1.56 1.91 2.30 Potential Difference (V + 0.001V) 0.526 0.877 1.404 1.893 2.324 2.796 Resistor 7 Voltage (V) 1 1.5 2 2.5 3 3.5 Current (mA + 0.01mA)

Middle

5.06 K? 6.96? Calculate the percentage error: Sample calculation: Percentage error of Resistor 2 % error = (Difference in measurements/Average of measurements)* 100% Difference in measurements = 0.828 K? - 1.202 K? = [-0.374 K?] = 0.374 K? Average of measurements = (0.828 K? + 1.202 K?) / 2 = 1.015 K? Percentage error = (0.374 K? / 1.015 K?) * 100% = 37% Percentage error of Resistor 7 = 0.2% Discussion: Ohmic materials are known to maintain a constant resistance regardless of the voltage. This explains why after plotting the graphs of Resistor 2 and Resistor 7 the end results are straight lines. This shows that the potential difference (voltage) and the current are directly proportional therefore maintaining an unchanging slope which represents the resistance.

Conclusion

This is why the slope of the line after the light has been lit is curved. Sources of Error: The manual adjustment of the voltage may have caused some error as we may have not adjusted it to the exact values required. If there were a more detailed and precise knob, it could reduce the error. Also, the wire were very rusty therefore acting as very poor conductors. The obvious solution would be to use newer wires. Conclusion: The purpose of this lab was to see how the potential difference and the electric current going through a conductor are related. By graphing the results it showed that they were directly proportional. This proved to be correct also for the cold resistivity of the light bulb, however the resistivity of the light bulb after it lit up contradicted Ohm's law as the resistivity did not remain constant.

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