This document discusses Kirchhoff's rules, which are techniques used to analyze electrical circuits. There are two main rules: 1) Kirchhoff's Junction Rule states that the total current entering a junction must equal the total current leaving it. 2) Kirchhoff's Loop Rule states that the total voltage change around any closed loop must be zero. The document provides examples of how to use these rules to determine voltages and currents in circuits by setting up equations based on the rules and solving them simultaneously.

1. KIRCHHOFF'S RULES- guide in analyzing complex networks
• Direct-current (DC) circuits-circuits in which the direction of the current does not change with time (e.g.
flashlights, automobile wiring system)
• Alternating current (AC) circuits - in which the current oscillates back and forth (e.g. household wiring system)
I. Review: Resistors in Series and Parallel
Find the equivalent resistance (Req)of the following circuits:
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fl. USing Kirchoffs Rules in finding the voltages and currents
Definition of Terms:
1) Junction - is a point in the circuit where three or more conductors meet. Junctions are also called nodes or
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2) loop - any closed conducting path. -";-
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From the circuit, which of the points labeled are considered as 1'"
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This technique is developed by the German physicist Gustav Robert a f
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A. Kirchhoff's Junction rule: The algebraic sum of the currents into any junction is zero. Based on the conservation
of charges: No charge can accumulate at a junction, so the total charge entering the junction per unit time must
equal the total charge leaving per unit time.
B. Kirchhoff's loop rule: The algebraic sum of the potential differences in any loop, including those associated with
emfs and those of resistive elements, must be equal to zero. The loop rule is a statement that the electrostatic
force is conservative. Suppose we go around a loop, measuring potential differences across successive circuit
elements as we go. When we return to the starting point, we must find Sign COIM:nt1ons for cmfs
that the algebraic sum of these differences is zero. ':,:.;. ~
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How to use Kirchhoffs Rules?
1. Assume a direction (CW or CCW) for current on each loop. Note: If the
actual direction of a particular quantity is opposite to your assumption,
the result will come out with a negative sign in your calculations.
2. Set up your equations based from the junction and loop rules' sign Sign convmtioos for resistors
convention. Get as ma:,y equations as your unknown variables.
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3. Solve the equations simultaneously to determine the unknowns. Be to CUIm1t direction: current directioo
careful with algebraic manipulations; one sign error will prove fatal to
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