What is the significance of resistance ratio, `rho_(300 K) // rho_(4.2K)` ?

Explanation

To understand the significance of the resistance ratio \( \frac{\rho_{300K}}{\rho_{4.2K}} \), we can break down the concept into a few key steps:

### Step 1: Define Resistance Ratio
The resistance ratio is defined as the ratio of the electrical resistivity of a metal at room temperature (approximately 300 K) to its resistivity at a much lower temperature (4.2 K, which is the temperature of liquid helium). Mathematically, it is expressed as:
\[ \text{Resistance Ratio} = \frac{\rho_{300K}}{\rho_{4.2K}} \]

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