Which of the following materials is/are commonly used to make the wires in thermocouples?

Explanation:

Thermocouples are temperature measurement devices that work based on the Seebeck effect, which is the generation of an electromotive force (EMF) when two dissimilar metals are joined together and exposed to a temperature gradient. The choice of materials for the wires in a thermocouple is critical because it determines the accuracy, temperature range, and durability of the thermocouple.

Correct Option Analysis:

The correct option is:

Option 1: Copper and Nickel

Thermocouples commonly use copper and nickel-based alloys, such as Constantan, due to their specific thermoelectric properties. One of the most widely used thermocouples, the Type T thermocouple, is made of copper and Constantan. This thermocouple is suitable for applications requiring moderate temperature measurements and is known for its high stability and accuracy.

Why Copper and Nickel (Constantan)?

• High Thermoelectric Sensitivity: The combination of copper and Constantan provides a high thermoelectric sensitivity, which ensures precise temperature readings.
• Wide Temperature Range: Type T thermocouples (Copper-Constantan) can measure temperatures in the range of -200°C to 350°C, making them versatile for many applications.
• Corrosion Resistance: Copper and nickel alloys are resistant to oxidation and corrosion, ensuring durability in various environments.
• Cost-Effective: These materials are relatively inexpensive compared to noble metals used in high-temperature thermocouples.
• Stability: The copper-Constantan combination exhibits excellent stability, particularly at low temperatures, making it a preferred choice in cryogenic applications.