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267 suppose your circuit laboratory has the following

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Unformatted text preview: . COMPREHENSIVE PROBLEMS 2.66 An electric heater connected to a 120-V source consists of two identical 0.4- elements made of Nichrome wire. The elements provide low heat when connected in series and high heat when connected in parallel. Find the power at low and high heat settings. 2.67 Suppose your circuit laboratory has the following standard commercially available resistors in large quantities: 1.8 20 300 24 k Rx 9V 56 k Using series and parallel combinations and a minimum number of available resistors, how would you obtain the following resistances for an electronic circuit design? (a) 5 (b) 311.8 (c) 40 k (d) 52.32 k 2.68 Switch Figure 2.126 2.70 In the circuit in Fig. 2.125, the wiper divides the potentiometer resistance between αR and (1 − α)R , 0 ≤ α ≤ 1. Find vo /vs . R For Prob. 2.69. A loudspeaker is connected to an ampliﬁer as shown in Fig. 2.127. If a 10- loudspeaker draws the maximum power of 12 W from the ampliﬁer, determine the maximum power a 4- loudspeaker will draw. Amplifier + Loudspeaker vs + − vo R Figure 2.127 aR − | v v Figure 2.125 | For Prob. 2.68. e-Text Main Menu 2.71 For Prob. 2.70. In a certain application, the circuit in Fig. 2.128 must be designed to meet these two criteria: (a) Vo /Vs = 0.05 (b) Req = 40 k | Textbook Table of Contents | Problem Solving Workbook Contents CHAPTER 2 If the load resistor 5 k meet the criteria. is ﬁxed, ﬁnd R1 and R2 to Basic Laws 2.73 R1 73 Two delicate devices are rated as shown in Fig. 2.130. Find the values of the resistors R1 and R2 needed to power the devices using a 24-V battery. 60-mA, 2-Ω fuse Vs + − + Vo − R2 5 kΩ R1 24 V, 480 mW Device 2 24 V Req R2 Device 1 9 V, 45 mW Figure 2.128 2.72 For Prob. 2.71. The pin diagram of a resistance array is shown in Fig. 2.129. Find the equivalent resistance between the following: (a) 1 and 2 (b) 1 and 3 (c) 1 and 4 4 20 Ω 10 Ω 40 Ω 10 Ω 80 Ω 1 Figure 2.129 2 For Prob. 2.72. v v | | For Prob. 2.73. 3 20 Ω | Figure 2.130 e-Text Main Menu | | Textbook Table of Contents | | Go to the Student OLC| Problem Solving Workbook Contents...
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