Calculating resistivity from relaxation time.

In summary, the formula for the conductivity of copper is given by \sigma = \frac{ne^2 \tau}{m}. To calculate the resistivity, the values for density, relaxation time, and mass of the electron can be substituted into the equation. The result obtained for copper was 1.6e-3 Ohmm. To calculate the Hall coefficient and magnetic field for copper using a hall probe, the thickness, hall voltage, and current measurements would need to be taken into account. It is unclear why the molar mass is not included in the equation.
  • #1
solas99
69
1
Given the following data on copper, how do i calculate the resistivity?

Relaxation time: 2.50e10-14s
Density: 8940Kgm-3
molar mass: 63.5g

is there an equation for it.
 
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  • #2
the formula for the conductivity [itex]\sigma[/itex] is given by

[itex]\sigma = \frac{ne^2 \tau}{m}[/itex] where [itex] n [/itex] is the density, [itex] e [/itex] is the electrical charge, [itex] \tau [/itex] is the relaxation time and [itex] m [/itex] mass of the electron. From here you should be able to find the resistivity.
 
  • #3
i did the calculation, i got: 1.6e-3 Ohmm is that correct, or am i missing something.
thanks for quick reply
 
  • #4
If we used the same metal (copper) in hall probe to measure the magnetic field, how can i calculate the hall coeficient of copper and the magnetic field acting on copper.

thickness 100um
hall voltage 0.1uV
current 1.5 A
 
  • #5
i am a bit confused, is there a reason why the molar mass isn't in the equation?
 

1. What is resistivity?

Resistivity is a measure of a material's ability to resist the flow of electric current. It is the inverse of conductivity and is typically represented by the Greek letter rho (ρ). It is measured in units of Ohm-meters (Ω·m).

2. How is resistivity calculated?

Resistivity can be calculated by dividing the product of the material's resistance (R) and cross-sectional area (A) by the length (L) of the material. This can be represented by the formula ρ = R·A/L. The resistance can be measured using a multimeter and the dimensions of the material can be measured using a ruler or calipers.

3. What is relaxation time?

Relaxation time is the time it takes for the electrons in a material to return to their equilibrium state after being disturbed by an external electric field. It is a property of the material and is related to its resistivity. Materials with shorter relaxation times tend to have higher conductivity.

4. How is resistivity related to relaxation time?

The relationship between resistivity (ρ) and relaxation time (τ) is given by the formula ρ = m·τ, where m is the electron mass and is a constant for a given material. This means that materials with longer relaxation times will have higher resistivity, while those with shorter relaxation times will have lower resistivity.

5. What factors can affect the accuracy of calculating resistivity from relaxation time?

There are several factors that can affect the accuracy of calculating resistivity from relaxation time. These include temperature, impurities in the material, and external electric fields. Additionally, the assumptions made in the calculation, such as assuming a constant relaxation time throughout the material, can also affect the accuracy of the result.

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