When Cu and Ge are cooled to -150 oC Then resistance of Cu _ and that of Ge _
Correct answer: D. Decreases, increases
- A. Increases, increases
- B. Decreases, decreases
- C. Increases, decreases
- D. Decreases, increases
Explanation
The resistance of copper decreases when cooled to -150 oC because it is a metal with a positive temperature coefficient of resistance; this means fewer thermal vibrations at lower temperatures allow electrons to move more freely. On the other hand, germanium, a semiconductor, has a negative temperature coefficient of resistance, leading to an increase in resistance at lower temperatures due to reduced intrinsic carrier concentration. Therefore, the correct answer is that the resistance of Cu decreases while that of Ge increases. The other options are incorrect because they do not take into account the fundamental differences in temperature response between metals and semiconductors.
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Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
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