The following figure shows a resistor R of 10Ω connected to a cell. An ammeter with coil resistance 1Ω is used to measure the current through the resistor.
圖片參考：http://img33.imageshack.us/img33/1086/91143912.png
(a) If the ammeter,connected in series with R reads 0.5A,calculate
(i) the potential difference across the ammeter(我計到是0.5V)
(ii) the potential difference across the 10Ω resistor(我計到是5V)
(iii) the e.m.f. of the cell(我計到是5.5V)
(b) The student soon finds the reading of the ammeter is not the current that he intended to measure
(i) calculate the expected the current(我計到是0.55A)
*(ii) explain the above finding.
*(c) what condition, regarding to the value of R is expected if the ammeter is to obtain a better measurement of the current? explain briefly.
phy電學
2010-12-11 4:54 am
回答 (1)
2010-12-11 7:19 am
✔ 最佳答案
(b)(ii) It is because of the "loading effect" of the ammeter. The introduction of the ammeter into the circuit alters the circuit resistance, and hence causes a change of current. Thus the current so measured is deviated from the value of the current that it should be.(c ) In order to obtain a better result, the resistance of the ammeter must be small compared with the value of the resistance R. In other words, R should be of resistance much higher than the resistance of the ammeter used.
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20101210000051KK01140