Temperature Coefficient of Resistance

The alpha (α) constant represents the resistance change per degree of temperature change and is known as the temperature coefficient of resistance. Like all materials have a specified resistance at 20° C, they vary their resistance by a specific amount with temperature change. It is a positive value for pure metals, increasing temperature resistance. This coefficient is a negative number for carbon, silicon and germanium elements, which means that resistance decreases with temperature. Resistance fluctuates very little with temperature changes in some metal alloys. 

The following formula can be used to estimate the resistance value for conductors:

R = Rref [1 + α(T-Tref)].

What is the temperature coefficient of resistance?

The temperature coefficient of resistance is commonly defined as the change in electrical resistance per degree of temperature change.

When it comes to the electrical resistance of conductors like gold, aluminium, silver and copper, it all comes down to the collision of electrons within the material. Increasing the temperature causes electron collisions to speed up and occur more frequently. As a result, the conductor’s resistance will rise with the temperature.

The formula for determining a conductor’s resistance is as follows at a temp other than what is indicated in a resistance table.

R = Rref [1 + α(T-Tref)]

Whereas,

R = conductor’s resistivity at a certain temperature t

Rref=Temperatures range from 20 to 0 degrees Fahrenheit

α = conductor material’s temperature coefficient of resistance

T=Temperature of the conductor in Celsius

Tref = The conductor material’s designated reference temperature (a)

The resistance value for conductor

To calculate a conductor’s resistance, divide its length (L) by its resistance (R). As a result, increasing its length will increase its resistance, while decreasing it will decrease it. Even the cross-sectional area (A) is directly related to its resistance.

Relationship of Temperature and Resistiveness

R0 is the conductor’s resistance at 0°C and RRT is the conductor’s resistance at T°C. Temperature and resistances R0 and RT are roughly correlated.

It is equal to RT = R0 [1 + (T-T0)]

It is equal to R0 [1+ (T)].

Consequently, the following equation shows that changes in electrical resistance due to temperature are mostly dependent on three variables:

The resistance value for conductor at a given temperature is called the initial resistance.

Increase in the outside air’s temperature.

The temperature coefficient of resistance.

Depending on the type of material, the value might vary. As the temperature rises, electrons in metals acquire greater kinetic energy, allowing them to collide with each other more frequently. It is well known that the resistivity of any substance is determined by its conductivity.

There are n charge carriers per volume n and a relaxation period between collisions determines the resistivity. As the metal’s temperature rises, the average electron velocity increases the number of collisions.

As a result, the period between repeated accidents is getting shorter and shorter. However, the increase in temperature has a small effect on the value of n, which means that the change only influences the change in resistivity.

Types of Temperature Coefficient Of Resistance

There are two primary types in terms of the temperature resistance value.

• Coefficient Of Resistance With Positive Temperature Coefficient

Due to a drop in, the material’s resistivity and resistance rise. As a result, metal has a positive temperature coefficient.

• Coefficient Of Resistance With Negative Temperature

The number of charge carriers per unit volume increases as the temperature rises in semiconductors and insulators. When temperatures rise, the drop in resistivity and resistance is compensated for by increasing n. Coefficient is a negative number for carbon, silicon and germanium elements.

The temperature coefficient of resistance is an important consideration

• Temperature affects the specific resistance of most conductive materials. For this reason, resistance measurements are always given in terms of temperature.

• A material with a positive coefficient suggests that its resistance increases with temperature. 

• Positive temperature coefficients of resistance are usual for pure metals. Certain metals can be alloyed to produce coefficients close to zero.

• A material with a negative coefficient indicates that its resistance reduces as the temperature rises. 

• It is common for semiconducting material to have a negative temperature coefficient of resistance.

Specific resistance table for coefficient temperature

Conclusion

Alpha (α) is a temperature coefficient of resistance representing the change in resistive change for each degree Celsius increase in temperature. Materials’ specific resistance changes with temperature, just as it does for all materials at 20° C. It is a positive value for pure metals, increasing temperature resistance. Alloy and pure metal temperatures are shown in the following table. 

As the temperature rises, electrons in metals acquire greater kinetic energy, allowing them to collide with each other more frequently. The formula to estimate resistance values for conductors is:

R = Rref [1 + α(T-Tref)].

Any substance’s resistivity can be calculated using the formula = m/nq2.