Physics

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Lab 6: Electrical Resistance

Objectives In this lab you will use PhET’s simulation Resistance in a Wire to study the dependence of electrical

resistance on the length, cross-sectional area, and the material of a wire.

Part 1: Dependence of Resistance on Length 1. Set the resistivity to 0.50 Ω cm and set the cross-sectional area to 7.50 cm2. Do not change

these values for this part.

2. Change the length of the wire from about 2 cm to 20 cm in steps of about 2 cm and record

the corresponding resistance. Record the actual values of the length that you are able to

achieve.

Length (cm)

Resistance (Ω)

3. Using Excel, graph a scatter plot of resistance versus length. Graph resistance on the vertical

axis and length on the horizontal axis. Include the best-fit curve on your graph as well as the

equation of the best-fit curve. Decide the type of curve to fit the data with based on

theoretical expectation.

4. Are your results as expected from theory?

Part 2: Dependence of Resistance on Cross-Sectional Area 1. Set the resistivity to 0.50 Ω cm and set the length to 10.00 cm. Do not change these values

for this part.

2. Change cross-sectional area from about 1 cm2 to 15 cm2 in steps of about 2 cm2 and record

the corresponding resistance. Record the actual values of the cross-sectional area that you

are able to achieve.

Area (cm2)

Resistance (Ω)

3. Using Excel, graph a scatter plot of resistance versus area. Graph resistance on the vertical

axis and area on the horizontal axis. Include the best-fit curve on your graph as well as the

equation of the best-fit curve. Decide the type of curve to fit the data with based on

theoretical expectation.

4. Are your results as expected from theory?

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Part 3: Dependence of Resistance on Resistivity 1. Set the length to 10.00 cm and set the cross-sectional area to 7.50 cm2. Do not change these

values for this part.

2. Change resistivity from 0.10 Ω cm to 1.00 Ω cm in steps of 0.10 Ω cm and record the

corresponding resistance.

Resistivity (Ω cm) 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Resistance (Ω)

3. Using Excel, graph a scatter plot of resistance versus resistivity. Graph resistance on the

vertical axis and resistivity on the horizontal axis. Include the best-fit curve on your graph

as well as the equation of the best-fit curve. Decide the type of curve to fit the data with

based on theoretical expectation.

4. Are your results as expected from theory?

Part 4: Superconductivity Electrical resistance depends on temperature as well. For many materials, when the temperature is

sufficiently low, resistivity vanishes, and the material becomes a superconductor.

This part does not involve the simulation. You need to do a little research instead.

Write a few paragraphs on superconductivity. Include these paragraphs at the end of the Data

Analysis and Discussion section of the report.