In the figure a voltmeter of resistance RV = 376 ? and an ammeter of resistance

Question

In the figure a voltmeter of resistance RV = 376 ? and an ammeter of resistance RA = 2.71 ? are being used to measure a resistance R in a circuit that also contains R0 = 100 ? and an ideal battery of emf ? = 12.0 V. Resistance R is given by V/i, where V is the potential across R and i is the ammeter reading. The voltmeter reading is V', which is V plus the potential difference across the ammeter. Thus, the ratio of the two meter readings is not R but only an apparent resistance R' = V'/i. If R = 113 ?, what are (a) the ammeter reading in milliamperes, (b) the voltmeter reading (in V), and (c) R'?

Explanation / Answer

Req=R0+Ra*Rv/(Ra+Rv)=102.7 so I=12/Req=.117 so V=12-I*R0=.3 A=V/Ra=.3/2.71=.116 so A=116 mA V'=.3 V R'=V/A=2.58

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