Which of the following resistivity$\text{ (ρ) }$ v/s temperature (T) curves is most suitable to be used in wire bound standard resistors?

Resistivity is independent of temperature for wire bound resistors

For wire-bound standard resistors, we need a material that exhibits:

1. Minimal variation of resistivity ($\rho$) with temperature ($T$) → Ensures stability and precision over a range of temperatures.
2. High resistivity → Reduces the required length of wire for a given resistance.
3. Good mechanical and thermal stability → Prevents fluctuations due to expansion/contraction.

Thus, the most suitable $\rho$ vs. $T$ curve should be a nearly horizontal line, indicating negligible dependence on temperature.