Question

Standard resistor is made from

• A. platinum
• B. manganin
• C. Silver
• D. nichrome

Hint:

Manganin is the go-to material for precision resistors due to its low temperature coefficient and high stability.

Answer 1

The Correct Option is B

Step 1: Understanding a standard resistor
Standard resistors are precision components used in laboratories and measurement equipment for calibration purposes. They are expected to exhibit stable resistance over a wide range of temperatures.
Step 2: Key properties required
The material used must have:
Very low temperature coefficient of resistance (TCR)
High long-term stability
Low thermal EMF against copper
Step 3: About Manganin
Manganin is an alloy of copper (Cu), manganese (Mn), and nickel (Ni), typically 84% Cu, 12% Mn, and 4% Ni. It has:
Negligible TCR (approx. $20 \times 10^{-6}/^\circ$C)
Very stable resistance over time
Step 4: Why other materials are not used
- Platinum: Very stable but too expensive. Used in RTDs, not in resistors.
- Silver: High conductivity but very poor thermal stability.
- Nichrome: Used in heaters and high-resistance applications due to high resistivity, not in standard resistors.