A student completes an experiment to find the electrical resistivity of a constantan wire.
She measures the resistance of different lengths of a constantan wire with a constant cross-sectional area of 2.0 × 10-7 m2 using a digital ohmmeter. She then calculates the resistivity of the constantan.
| Attempt | Length (m\text{m}m) | Measured Resistance (Ω\OmegaΩ) | Calculated Resistivity (10−7 Ω m10^{-7}\ \Omega\text{ m}10−7 Ω m) |
|---|---|---|---|
| 1 | 0.20 | 0.52 | 5.2 |
| 2 | 0.40 | 1.08 | 5.4 |
| 3 | 0.80 | 2.24 | 5.6 |
a.[2]
Calculate the mean resistivity of the constantan wire.
b.[3]
Describe the conclusions that can be drawn from the data.
c.[2]
The actual value for the resistivity of constantan is 4.9 × 10-7 Ω m.
Explain why the mean resistivity calculated in (a)(i) is higher than the actual value.
d.[4]
Write down two problems with this experiment and suggest how they could be solved. Use the diagram and results table to help you.