8 ohms 320 3 320 v v note that ra5003 and rb5003

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Unformatted text preview: 08.8 ohms. (940 3) + (500 3) (3)(1440) | Textbook Table of Contents | Problem Solving Workbook Contents 108.8 Ω a a Req 293.8 Ω Req Req 108.8 Ω b b Therefore, R eq = 293.8 (108.8 + 108.8) = 293.8 217.6 = R eq = 125.01 ohms (293.8)(217.6) 63930 = 293.8 + 217.6 511.4 Convert the T connected resistors, labeled in the circuit below, to ∆ connected resistors. (b) a 100 Ω Req 100 Ω 100 Ω 100 Ω 100 Ω 100 Ω b It can be shown that 100 Ω 300 Ω 100 Ω 300 Ω 100 Ω 300 Ω So, the circuit becomes 100 Ω 100 Ω a 300 Ω Req 300 Ω 100 Ω 300 Ω 100 Ω 300 Ω 100 Ω 300 Ω 300 Ω 100 Ω b | v v 100 Ω | e-Text Main Menu 100 Ω | Textbook Table of Contents | Problem Solving Workbook Contents Now, each of the slanted branches of the ∆ connection is in parallel with a 100 Ω resistor. 300 || 100 = (300)(100) 30000 = = 75 ohms 300 + 100 400 This leads to the following circuit. 100 Ω 100 Ω a 75 Ω Req 300 Ω 75 Ω 300 Ω 75 Ω 75 Ω b 100 Ω 100 Ω Clearly, now we have two places in the circuit where a 300 ohm resistor is in parallel with the series combination of two 75 ohm resistors. 300 || (75 + 75) = 300 || 150 = (300)(150) 45000 = = 100 ohms 300 + 150 450 This simplifies the circuit to 100 Ω 100 Ω a Req 100 Ω 100 Ω b 100 Ω 100 Ω It is evident that we have R eq = 100 + 100 (100 + 100 + 100) + 100 or R eq = 100 + 100 300 + 100 where we have already shown that 100 300 = 75 . Therefore, R eq = 100 + 75 + 100 | v v R eq = 275 ohms | e-Text Main Menu | Textbook Table of Contents | Problem Solving Workbook Contents APPLICATIONS Problem 2.18 Given a real voltmeter with an internal resistance of R m , determine its effect when measuring the voltage across R 2 in Figure 2.1. R1 + VS + − VR2 Rm R2 − Figure 2.1 Carefully DEFINE the problem. Each component is labeled, indicating value and polarity. The problem is clear. PRESENT everything you know about the problem. The voltmeter measures the voltage across a component and is the...
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