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PHY AL MC 99#16

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AL MC 99#16 唔明 statement (2)..

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首先, 要明白題目中所指的 voltmeter 同 ammeter 為 "real" 而非 ideal. 所以: Voltmeter: Draws a little (but NOT zero) current Ammeter: Has a little (but NOT zero) p.d. across it. Under such connection: The voltmeter records the actual p.d. across R, but the ammeter records the total current of R and voltmeter. Therefore, the ratio of voltmeter and ammeter readings becomes: R' = V/(IV + IR) where IV and IR are currents through the voltmeter and R respectively. But the actual value of R should be: R = V/IR Therefore the ratio calculated is in fact smaller than the value of R.

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