* Question
What are the two main factors that cause resistance changes due to changes in ambient temperature?
* Answer
The two main factors that cause resistance changes in a material due to changes in ambient temperature are:
1. Intrinsic Property of the Material:
– Temperature Coefficient of Resistance (TCR): This is an intrinsic property of the material that defines how its resistance changes with temperature. For most conductive materials, the resistance increases with an increase in temperature (positive TCR), while for some materials like semiconductors, the resistance decreases with an increase in temperature (negative TCR). The relationship can be expressed as:
R(T)=R0[1+α(T−T0)]
whereR(T)s the resistance at temperatureT, R0 is the resistance at reference temperature T0, and αis the temperature coefficient of resistance.
2. Physical Changes in the Material:
– Thermal Expansion and Contraction: As temperature changes, materials expand or contract. This physical change can alter the dimensions of the material (length, cross-sectional area), which in turn affects the resistance. For a conductor, resistance ( R ) is given by:
R =ρL/A
whereρ is the resistivity of the material, L is the length, and A is the cross-sectional area. Thermal expansion can increase L and/or decrease A, leading to changes in resistance.
These factors combine to influence the overall change in resistance with temperature. Understanding these effects is crucial for designing and using materials in temperature-sensitive applications, such as in temperature sensors (thermistors), precision resistors, and other electronic components.
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