Question

Basic Electricity - Temperature coefficient of resistance of different metals

Answer 1

The temperature coefficient of resistance (TCR) is a measure of how much the resistance of a material changes with changes in temperature. It is typically expressed in terms of parts per million per degree Celsius (ppm/°C). Different metals have different TCR values, which affect their behavior in electrical circuits as temperature changes. Here are the TCR values for some common metals:

Copper (Cu):
TCR = 0.00393 ppm/°C (at 20°C)

Aluminum (Al):
TCR = 0.0039 ppm/°C (at 20°C)

Silver (Ag):
TCR = 0.0038 ppm/°C (at 20°C)

Gold (Au):
TCR = 0.0034 ppm/°C (at 20°C)

Iron (Fe):
TCR = 0.0065 ppm/°C (at 20°C)

Nickel (Ni):
TCR = 0.006-0.007 ppm/°C (at 20°C)

Tungsten (W):
TCR = 0.0045 ppm/°C (at 20°C)

Platinum (Pt):
TCR = 0.00392 ppm/°C (at 0°C)

Constantan (CuNi):
TCR = ~0.00001 ppm/°C (close to zero, used in precision resistors)

These values are approximations and can vary slightly based on the specific composition of the metal alloy, impurities, and temperature range. It's important to note that materials with higher TCR values will experience larger changes in resistance as temperature changes. This property can be both advantageous and problematic depending on the application.

For example, in temperature-sensitive applications, using materials with low TCR values like Constantan can help maintain stable resistances over varying temperatures. On the other hand, in devices where temperature compensation is needed, materials with specific TCR values might be intentionally chosen to achieve the desired functionality.

Remember that TCR is an intrinsic property of the material itself and is independent of the shape or size of the conductor. It's a fundamental characteristic that engineers and designers consider when selecting materials for various electrical and electronic applications.