Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 27 - Circuits - Problems - Page 797: 36d

Answer

The direction of the current through resistor 2 is to the right.

Work Step by Step

Let $i_1$ be the current through $R_1$ and let's assume the direction of the current is down. Let $i_2$ be the current through $R_2$ and let's assume the direction of the current is to the right. Let $i_3$ be the current through $R_3$ and let's assume the direction of the current is to the left. Using the junction rule: $i_1 = i_2+i_3$ $i_3 = i_1-i_2$ Using the loop rule counterclockwise around the right loop: $12.0-300~i_3-100~i_1 = 0$ $12.0-300~(i_1-i_2)-100~i_1 = 0$ $12.0-400~i_1+300~i_2 = 0$ $24.0-800~i_1+600~i_2 = 0$ Using the loop rule clockwise around the left loop: $6.00-200~i_2-100~i_1 = 0$ $18.0-600~i_2-300~i_1 = 0$ We can add these two equations to find $i_1$: $42.0-1100~i_1 = 0$ $i_1 = \frac{42.0}{1100}$ $i_1 = 38.2~mA$ The current through resistance 1 is $~~38.2~mA$ We can find $i_2$: $6.00-200~i_2-100~i_1 = 0$ $6.00-200~i_2-100~(38.2~mA) = 0$ $200~i_2 = 2.18$ $i_2 = \frac{2.18}{200}$ $i_2 = 10.9~mA$ The current through resistance 2 is $~~10.9~mA$ We assumed that the direction of the current through resistor 2 is to the right, and we found the current to be $10.9~mA$ Since the value we found for $i_2$ is positive, the direction of the current through resistor 2 is to the right.
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