Unformatted text preview: . COMPREHENSIVE PROBLEMS
2.66 An electric heater connected to a 120V 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. eText 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 24V battery.
60mA, 2Ω 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 eText Main Menu   Textbook Table of Contents   Go to the Student OLC Problem Solving Workbook Contents...
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 Resistor, Electrical impedance, Series and parallel circuits, DC Circuits, eText Main Menu

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