电路基础(第三版)alexander and sadiku著 课后题答案chapter 02.docxVIP

Chapter 2, Problem 1. The voltage across a 5-kΩ resistor is 16 V. Find the current through the resistor. Chapter 2, Solution 1 v = iR i = v/R = (16/5) mA = 3.2 mA Chapter 2, Problem 2. Find the hot resistance of a lightbulb rated 60 W, 120 V. Chapter 2, Solution 2 p = v2/R → R = v2/p = 14400/60 = 240 ohms Chapter 2, Problem 3. A bar of silicon is 4 cm long with a circular cross section. If the resistance of the bar is 240 Ω at room temperature, what is the cross-sectional radius of the bar? Chapter 2, Solution 3 For silicon, ρ = 6.4x102 Ω-m. A = π r 2 . Hence, R = ρ L = ρ L → r2 = ρ L = 6.4x102 x 4x10?2 = 0.033953 π r2 π R π x240 A r = 0.1843 m Chapter 2, Problem 4. Calculate current i in Fig. 2.68 when the switch is in position 1. Find the current when the switch is in position 2. Chapter 2, Solution 4 i = 3/100 = 30 mA i = 3/150 = 20 mA PROPRIETARY MATERIAL. ? 2007 The McGraw-Hill Companies, Inc. All rights reserved. No part of this Manual may be displayed, reproduced or distributed in any form or by any means, without the prior written permission of the publisher, or used beyond the limited distribution to teachers and educators permitted by McGraw-Hill for their individual course preparation. If you are a student using this Manual, you are using it without permission. Chapter 2, Problem 5. For the network graph in Fig. 2.69, find the number of nodes, branches, and loops. Chapter 2, Solution 5 n = 9; l = 7; b = n + l – 1 = 15 Chapter 2, Problem 6. In the network graph shown in Fig. 2.70, determine the number of branches and nodes. Chapter 2, Solution 6 n = 12; l = 8; b = n + l –1 = 19 Chapter 2, Problem 7. Determine the number of branches and nodes in the circuit of Fig. 2.71. 1 Ω 4 Ω 12 V + 8 Ω 5 Ω 2 A _ Figure 2.71 For Prob. 2.7. Chapter 2, Solution 7 6 branches and 4 nodes. PROPRIETARY MATERIAL. ? 2007 The McGraw-Hill Companies, Inc. All rights reserved. No part of this Manual may be displayed, reproduced or distributed in any form or by any means, with