Which metal is having excellent temperature vs resistance linearity used for making resistance thermometer? Platinum Copper Nickel None of these

To determine which metal exhibits excellent temperature versus resistance linearity for making resistance thermometers, let's analyze the options:

1. Platinum: Platinum is widely recognized for its exceptional linearity in resistance change with temperature. It is the most commonly used material in resistance temperature detectors (RTDs) due to its stable electrical properties across a wide temperature range.

2. Copper: While copper has a good conductivity and is used in various applications, it does not exhibit the same level of linearity in resistance change with temperature compared to platinum. It has a significant temperature coefficient of resistance but is less stable than platinum over wider temperature ranges.

3. Nickel: Nickel can also be used in some thermometers and has a reasonable temperature coefficient, but it does not provide the same reliability and linearity as platinum.

4. None of these: This option suggests that none of the above metals are suitable, which is incorrect given the properties of platinum.

Conclusion

Given the analysis, the metal with excellent temperature versus resistance linearity used for making resistance thermometers is Platinum.