Chapter 28139(e)Increasing resistor 3 increases the equivalent resistance of the entire circuit. The current inthe circuit, which is the current through resistor 1, decreases. This decreases the potentialdifference across resistor 1, increasing the potential difference across the parallelcombination. With a larger potential difference the current through resistor 4 is increased.With more current through 4, and less in the circuit to start with, the current throughresistors 2 and 3 must decrease. To summarize, IIII4123increases and and decrease,,.(f)If resistor 3 has an infinite resistance it blocks any current from passing through that branch,and the circuit effectively is just resistor 1 and resistor 4 in series with the battery. The circuitnow has an equivalent resistance of 4R. The current in the circuit drops to 34of the originalcurrent because the resistance has increased by 43. All this current passes through resistors 1and 4, and none passes through 2 or 3. Therefore IIII123434034====.Section 28.3Kirchhoff’s RulesP28.20+−−=15 07 002 00 5 0001..afafafI500 7001=I
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