This preview shows page 1. Sign up to view the full content.
Unformatted text preview: 106 CHAPTER 18 18.6 The equivalent resistance of the parallel combination of three resistors is
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:
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 .
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