Chapter 27, Problem 56P

In Fig. 27-62. a voltmeter of resistance R_v = 300 Ω and an ammeter of resistance R_A = 3.00 Ω are being used to measure a resistance R in a circuit that also contains a resistance R₀ = 100 Ω and an ideal battery of emf ℰ = 12.0 V. Resistance R is given by R = Vli. where V is the voltmeter reading and i is the current in resistance R. However, the ammeter reading is not i but rather i', which is i plus the current through the voltmeter. Thus, the ratio of the two meter readings is not R but only an apparent resistance R’ = V/i’. If R = 85.0 Ω, what are (a) the ammeter reading, (b) the voltmeter reading, and (c) R’? (d) If R_v is increased, does the difference between R’ and R increase, decrease, or remain the same?

Figure 27-62 Problem 56.