Lesson 7 - Solving Circuits with Kirchhoff's Laws - Part 1
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Overview of this Lesson
In this lesson, we use Kirchhoff's Voltage Law (KVL) together with Kirchhoff's Current Law (KCL) to solve circuit problems. The student is taught how to know when to use one law instead of the other, and also when it is necessary to use both laws at the same time to solve the problem.
Kirchoff's Current Law is used at nodes in a circuit where 3 or more circuit elements are interconnected. We use the KCL law to write the sum of the currents entering a node to be equal to the currents leaving a node. We use the Kirchhoff Voltage Law (KVL) to trace loops in the circuit and sum up the voltage drops across all elements in the loop. This sum of the voltage drops in a loop must always be zero in a circuit and is essentially a statement of the law of conservation of energy.
Particular focus in this lesson is spent in reinforcing the sign convention to the student which is used when writing the KCL and KVL equations. We begin with simpler circuits and progress gradually to the more complex circuits in order to give the student a solid foundation with using Kirchhoff's laws to solve circuit problems.