Question

Which of the following resistivity (\(\rho\)) vs temperature (T) curves is most suitable to be used in wire-bound standard resistors?

• A.
• B.
• C.
• D.

Hint:

In wire-bound standard resistors, resistivity is constant across temperature changes.

Answer 1

The Correct Option is A

In wire-bound standard resistors, it is crucial to have a stable resistivity with changes in temperature to ensure accurate and consistent resistance values. This implies that the ideal resistivity (\(\rho\)) vs. temperature (T) curve should show minimal variation in resistivity when temperature changes. The curve that best fits this requirement would be one that is relatively constant, i.e., a horizontal line, indicating resistivity remains the same despite temperature fluctuations.

Looking at the options, the curve in represents a situation where resistivity does not change noticeably with temperature. Therefore, this is the most suitable choice for wire-bound standard resistors, as it suggests a resistivity that is largely independent of temperature changes, maintaining reliability and precision in resistance values.

Answer 2

Concept: 
For wire-bound standard resistors, the material used should have a very small temperature coefficient of resistivity — meaning its resistivity should remain almost constant with change in temperature.

Explanation:
If resistivity \( \rho \) changes significantly with temperature \( T \), the resistance of the wire will also vary, making the resistor unsuitable as a standard (since it won’t give a constant resistance value).

Thus, the most suitable \( \rho \)-vs-\( T \) curve is the one where \( \rho \) remains nearly constant over a wide range of temperature (a nearly horizontal line).

Hence, the correct option is:
Option 1 — the graph showing almost constant resistivity with temperature.