By varying the position of the potentiometer’s wiper W in the circuit of Fig. P7.3 we can select any value of b from 0 (W all the way down) to 1 (W all the way up). For instance, with W set 1y4 of the...

By varying the position of the potentiometer’s wiper W in the circuit of Fig. P7.3 we can select any value of b from 0 (W all the way down) to 1 (W all the way up). For instance, with W set 1y4 of the way up so that the portion of the potentiometer’s resistance below W is Rbelow 5 2.5 kV and that above W is Rabove 5 7.5 kV, we get b 5 2.5y(2.5 1 7.5) 5 0.25. (a) Let vi 5 1.0 V. If it is found that vo 5 1.0 V with W all the way down, what is vo with W all the way up? With W halfway? (b) If vi is held constant and it is found that the circuit gives vo 5 26 V with W all the way up, and vO 5 211 V with W halfway, fi nd a and vi . (c) Derive an expression for b in terms of 1yA and 1ya, and then fi nd the wiper’s position that will result in voyvi 5 10 V/V in the following two cases: a 5 ` and a 5 100 V/V.