8_Ch 18 College Physics ProblemCH18 Direct-Current Circuits

8_Ch 18 College - 106.6 The equivalent resistance of the parallel combination of three resistors is −1 1 1 1 Rp = = 3.0 Ω 18 Ω 9.0 Ω 6.0

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Unformatted text preview: 106 CHAPTER 18 18.6 The equivalent resistance of the parallel combination of three resistors is −1 1 1 1 Rp = + + = 3.0 Ω 18 Ω 9.0 Ω 6.0 Ω Hence, the equivalent resistance of the circuit connected to the 30 V source is Req = R12 + Rp = 12 Ω + 3.0 Ω = 15 Ω 18.7 If a potential difference is applied between points a and b, the vertical resistor with a free end is not part of any closed current path. Hence, it has no effect on the circuit and can be ignored. The remaining four resistors between a and b reduce to a single equivalent resistor, Req = 2.5R , as shown below: R a 18.8 R R R b a R R R/2 b a 2.5R b (a) The rules for combining resistors in series and parallel are used to reduce the circuit to an equivalent resistor in the stages shown below. The result is Req = 5.13 Ω . 10.0 W 3.00 W 4.00 W 10 — 3 3.00 W Figure 1 Figure 2 W 3.00 W 3.00 W 4.00 W 3.00 W 5.00 W 3.00 W 22 — 3 W 66 — 31 W Req = 5.13 W 3.00 W Figure 3 Figure 4 (b) From P = ( ∆V ) Req , the emf of the power source is 2 ∆V = P⋅Req = ( 4.00 W ) ( 5.13 Ω ) = 4.53 V Figure 5 ...
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This note was uploaded on 12/09/2011 for the course PHYS 2020 taught by Professor Staff during the Fall '10 term at FIU.

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