A piece of copper and other of germanium arecooled from the room tempe...
Cooling Effect on Resistance of Copper and GermaniumIntroduction
When a material is cooled, its resistance may either increase or decrease depending on its temperature coefficient of resistance (TCR). The TCR is a measure of how much the resistance of a material changes with temperature. In this case, we are cooling a piece of copper and a piece of germanium from room temperature to 80 K, and we need to determine the effect on their resistances.
Explanation
1. Copper:Copper has a positive TCR, which means that its resistance increases with increasing temperature. Therefore, when copper is cooled from room temperature to 80 K, its resistance will increase. This is because as the temperature decreases, the lattice vibrations in the copper crystal lattice decrease, leading to a decrease in the mobility of free electrons and an increase in resistance.
2. Germanium:Germanium, on the other hand, has a negative TCR, which means that its resistance decreases with increasing temperature. Therefore, when germanium is cooled from room temperature to 80 K, its resistance will decrease. This is because as the temperature decreases, the lattice vibrations in the germanium crystal lattice decrease, leading to an increase in the mobility of charge carriers and a decrease in resistance.
Conclusion
In conclusion, when a piece of copper and a piece of germanium are cooled from room temperature to 80 K, the resistance of copper will increase while the resistance of germanium will decrease. This can be attributed to the different temperature coefficients of resistance of the two materials.