Multiple-Choice Homework Problem 13.7 The figure shows two light bulbs, BA and B

Question

Multiple-Choice Homework Problem 13.7 The figure shows two light bulbs, BA and BB in parallel connected across a battery. When the switch is closed a third bulb, BC , is connected in parallel with the first two bulbs. Is the current through the battery before the switch is closed, Ibef ore, greater, the same as, or less than the current through the battery after the switch is closed, Iaf ter. BA BB BC Select One of the Following: 2 (a) Ibefore > Iafter (b) Ibefore < Iafter (c) Ibefore = Iafter

Multiple-Choice Homework Problem 13.8 For the resistor network to the right, R1 = 10?, R2 = 20?, R3 = 25?, R4 = 15?, R5 = 5?, and ?V0 = 20V . Compute the current through R3. Select One of the Following: (a) 0.67A (b) 0.33A (c) 0.27A (d) 5.1A (e) 3.0A

Explanation / Answer

1. I before < I later since now bulb BC also draws current from battery in addition to what BA and BB were drawing earlier.

2. Equivalent resistance os the circuit = R4+ (R1+R2)*(R3+R5)/(R1+ R2 + R3+R5)

Equivalent resistance = 30 ohms.

Net current drwan from battery I = 20/30 = 2/3 A

Current through R3 = I(R1+R2)/(R1+R2+R3+R5) = (2/3)*(15+15)/(15+15+25+5) = 1/3 A = 0.33 A

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