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An extension of this analysis to three or more resistors in parallel gives (28.8) We can see from this expression that the inverse of the equivalent resistance of two or more resistors connected in parallel is equal to the sum of the inverses of the Household circuits are always wired such that the appliances are connected in par- allel. Each device operates independently of the others so that if one is switched off, 1 R eq # 1 R 1 % 1 R 2 % 1 R 3 % ( ( ( SECTION 28.2 • Resistors in Series and Parallel 865 The equivalent resistance of several resistors in parallel Quick Quiz 28.5 In Figure 28.4, imagine that we add a third resistor in series with the first two. Does the current in the battery (a) increase, (b) decrease, or Quick Quiz 28.6 In Figure 28.6, imagine that we add a third resistor in parallel with the first two. Does the current in the battery (a) increase, (b) decrease, Quick Quiz 28.7 With the switch in the circuit of Figure 28.7 open (left), there is no current in R 2 . There is current in R 1 and this current is measured with the ammeter at the right side of the circuit. If the switch is closed (Fig. 28.7, right), there is 2 . What happens to the reading on the ammeter when the switch is closed? (a) the reading goes up; (b) the reading goes down; (c) the reading does not change. Switch open R 1 R 2 Switch closed A R 1 R 2 A Figure 28.7 (Quick Quiz 28.7) What happens when the switch is closed? Conceptual Example 28.3 Landscape Lights A homeowner wishes to install 12-volt landscape lighting on the cable at 10-foot intervals, so the light fixtures are in |