* Resistivity and Temperature: The electrical resistivity of metals decreases as temperature decreases. This is because the thermal vibrations of the atoms in the metal, which hinder the flow of electrons, are reduced at lower temperatures.
* Finding Resistivity: To get the precise resistivity value, you'd need to consult a table or graph specifically for copper at 77 K. However, we can give you a general idea:
* Room Temperature Resistivity: The resistivity of copper at room temperature (20°C or 293 K) is approximately 1.68 x 10^-8 Ωm.
* Lowering Temperature: At 77 K, the resistivity will be significantly lower. The exact value depends on the specific purity of the copper and other factors.
Estimating Resistivity at 77 K:
While we can't give you an exact value without a specific table, here's how you can estimate:
1. Temperature Coefficient: Copper has a temperature coefficient of resistivity of approximately 0.0043 per degree Celsius. This means that resistivity decreases by 0.0043% for every 1 degree Celsius decrease in temperature.
2. Temperature Difference: The temperature difference between room temperature (293 K) and 77 K is 216 K.
3. Approximate Reduction: The resistivity at 77 K would be roughly 0.0043 * 216 = 0.93 times lower than at room temperature.
4. Estimate: A rough estimate would be 1.68 x 10^-8 Ωm * 0.07 = ~ 1.2 x 10^-8 Ωm.
Important: This is a very rough estimate. The actual resistivity at 77 K will be lower than this, and a precise value can only be obtained from reliable sources.
To find the accurate resistivity:
* Look for a table or graph: Search for "resistivity of copper at 77 K" or "copper resistivity vs. temperature" online.
* Consult a materials science textbook: They often contain tables of material properties.
Remember, the exact resistivity of copper at 77 K will depend on the specific sample and its purity.
