Question 18.4: APPLYING KIRCHHOFF'S RULES GOAL Use Kirchhoff's rules to fin...
APPLYING KIRCHHOFF’S RULES
GOAL Use Kirchhoff’s rules to find currents in a circuit with three currents and one battery.
PROBLEM Find the currents in the circuit shown in Figure 18.15 by using Kirchhoff’s rules.
STRATEGY There are three unknown currents in this circuit, so we must obtain three inde pendent equations, which then can be solved by substitution. We can find the equations with one application of the junction rule and two applications of the loop rule. We choose junction c. (Junction d gives the same equation.) For the loops, we choose the bottom loop and the top loop, both shown by blue arrows, which indicate the direction we are going to traverse the circuit mathematically (not necessarily the direction of the current). The third loop gives an equation that can be obtained by a linear combination of the other two, so it provides no additional information and isn’t used.
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