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Simple Nature - Light and Matter

Simple Nature - Light and Matter

Simple Nature - Light and Matter

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Interpreting this result, we see that it comes from two effects thatpartially cancel. Closing the switch reduces the equivalent resistanceof the circuit by giving charge another way to flow, <strong>and</strong>increases the amount of current drawn from the battery. ResistorB, however, only gets a 1/3 share of this greater current, not1/2. The second effect turns out to be bigger than the first, <strong>and</strong>therefore the current through resistor B is lessened over all.Discussion QuestionA We have stated the loop rule in a symmetric form where a seriesof voltage drops adds up to zero. To do this, we had to define a st<strong>and</strong>ardway of connecting the voltmeter to the circuit so that the plus <strong>and</strong> minussigns would come out right. Suppose we wish to restate the junction rulein a similar symmetric way, so that instead of equating the current comingin to the current going out, it simply states that a certain sum of currents ata junction adds up to zero. What st<strong>and</strong>ard way of inserting the ammeterwould we have to use to make this work?This chapter is summarized on page 956. Notation <strong>and</strong> terminologyare tabulated on pages 941-942.Section 9.2 Parallel <strong>and</strong> Series Circuits 543

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