Conductors:
* Increased temperature leads to increased resistance.
* Reason: As temperature rises, the atoms in the conductor vibrate more vigorously. This increased vibration makes it harder for electrons to move freely through the material, leading to higher resistance.
* Example: Copper wire has a higher resistance when it's hot compared to when it's cold.
Semiconductors:
* Increased temperature leads to decreased resistance.
* Reason: Semiconductors have a unique band structure where electrons need a certain energy to jump into the conduction band and participate in current flow. As temperature increases, more electrons gain enough energy to jump into the conduction band, increasing the number of charge carriers and reducing resistance.
* Example: A silicon transistor conducts more current at higher temperatures.
The Temperature Coefficient of Resistance (α)
The relationship between temperature and resistance is quantified by the temperature coefficient of resistance (α). This value is specific to each material and indicates how much the resistance changes per degree Celsius (or Fahrenheit).
* Positive α: For conductors, α is positive, meaning resistance increases with temperature.
* Negative α: For semiconductors, α is negative, meaning resistance decreases with temperature.
Factors Affecting Temperature Dependence:
* Material: Different materials have different temperature coefficients.
* Purity: Impurities in a material can affect its resistance and temperature dependence.
* Temperature range: The relationship between resistance and temperature is not always linear and can vary at different temperature ranges.
Practical Applications:
* Temperature sensors: The change in resistance with temperature is used in devices like thermistors and RTDs (Resistance Temperature Detectors) for temperature measurement.
* Circuit design: Temperature effects on resistance need to be considered in circuit design to ensure reliable performance.
In summary, temperature has a significant effect on the resistance of conducting materials, with conductors showing increased resistance with increasing temperature and semiconductors showing decreased resistance. The temperature coefficient of resistance helps quantify this relationship.
