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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 2.3 Potential Difference (V + 0.001V) 0.526 0.877 1.404 1.893 2.324 2.796

Middle

2.359

2.793

Resistor 2 = 1.202 KΩ

Resistor 7 = 5.07 KΩ

## Light Bulb

Before lighting up:

 Voltage (V+ 0.0001V) 0.0069 0.0781 0.578 0.656 0.759 Current (mA+ 0.01mA) 0.9 10.5 81.3 92.4 109.7

The light bulb lit up at:

 Voltage (V+ 0.0001V) 1.001 Current (mA+ 0.01mA) 149.3

After lighting up:

 Voltage (V+ 0.0001V) 1.609 1.831 2.116 Current (mA + 0.01mA) 182.3 200 223.5

Data Analysis:

Calculate the slope of each graph:

Sample Calculation:

Slope of Resistor 2 = (y2 – y1) / (x2 – x1)

= (2.30 V – 0.42V )/(2.796mA – 0.526mA)

= (2.30 V – 0.42V )/(0.

Conclusion

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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