Physics mc 一問

2007-05-24 7:11 pm

The lead acid accumulator is used as the driver cell of the potentiometer because
A. it can provide a large current
B. it is rechargeable and is therefore economical
C. it has negligible internal resistance
D. it can deliver a large amount of electrical energy

I want to know why the answer is C. If possible , please explain why the other three answers are incorrect. Thank you~

回答 (1)

天同

2007-05-25 1:45 am

✔ 最佳答案

The most important thing in a potentiometer (or a voltage divider) is that you have to know the emf of the driving cell in order to calibrate the potentiometer.
If the driving cell is of considerable internal resistance, then the voltage across the potentiometer will not be equal to the emf , as there is a [loss voltage] (voltage drop across the cell internal resistance) due to the presence of internal resistance in the the driving cell. This would introduce error in the voltage obtained from the potentiometer.
The other options are wrong becuae they are irrelevant.

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