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[Phy] 97 mc 31 (last one)

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97 mc 31 (last one)

搵吾到圖,所以畫左出黎...係下邊,問題我打出黎

in above circuit, X and Y are identical heaters.The ammeter has negligible resistance
while the voltmeter has very high resistance.When switch S is closed, ammeter records
a reading but the voltmeter reading is zero.Which of the following provides a possible explanation?

A.the heater X burns out.
B.the heater Y burns out.
C.the heater X is short-circuited.
D.the heater Y is short-circuited.
E.the battery is short-circuited.


ans:C
有2條問題
1.點解a吾得 ?
2.如果X burns out 個情況會點?

THANKYOU
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回覆 #1 ah﹏中 的帖子

如果X burns out, 咁current剩係流向voltmeter, 因為voltmeter has a very high resistance, by V=IR, current會變到好細~
如果heater X is short-circuited, 咁所有電流會經short-circuited heater而唔係voltmeter, 所以voltmeter會無reading~

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burns out左ammeter應該冇reading而voltmeter reading應為battery既emf
有錯請更正

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X burns out can be treated as the wire breaks
thus all current flows through the voltmeter and there is reading of the voltmeter

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