8_Chapter 18 HomeworkCH18 Direct-Current Circuits

# 8_Chapter 18 HomeworkCH18 Direct-Current Circuits - 106.6...

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

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 ...
View Full Document

## This document was uploaded on 10/20/2011.

Ask a homework question - tutors are online