Analyzing Circuits Kirchoff’s Rules

Kirchoff’s Voltage Rule The total potential supplied by the source must be “used up” by the components of the circuit. The sum of the potential drops across each component in a series circuit will be equal to the total potential supplied by the source The electrons going through parallel branches will each experience the same drop in potential by the time they meet up again in the main circuit Kirchoff’s Voltage Rule

Kirchoff’s Current Rule The total current passing through a circuit depends on the total resistance. Current leaving the potential source is the same as the current entering the potential source (it’s not “used up”) Current must pass equally through all components in series with each other When current reaches a junction, it will split. The sum of the currents entering a junction will be equal to the sum of the currents exiting a junction Kirchoff’s Current Rule

Analyzing combination circuits Kirchhoff’s Rules make analyzing a complex circuit simply a logic puzzle, and not a difficult one, either! Analyzing combination circuits

Problem Solving Stragegy Resistor: Resistance /W Potential Drop / V Current / A R1: R2: R3: R4: R5: Step 1: Create a table of Resistance, voltage, and current Problem Solving Stragegy

Problem Solving strategy Step 2: Determine effective resistance and total current for the entire circuit Problem Solving strategy

Problem Solving strategy Step 3: All resistors that are in series (in the main flow of current) will carry the total current you just calculated. Knowing that, you can determine the potential drop across each item that is in series in the main flow. Problem Solving strategy

Problem Solving Strategy You now have the highlighted boxes filled in  How do you determine the potential drop for the parallel branches? Which resistor(s) have an individual potential drop equivalent to this value? Resistor: Resistance /W Potential Drop / V Current / A R1: R2: R3: R4: R5: Problem Solving Strategy

Problem Solving strategy Step 4: Determine the potential drop across each parallel branch Note: if there is more than 1 set of parallel branches (not in this example…), then simply find the effective resistance of the set of branches, use the total current, and find the potential drop for that set of branches. Problem Solving strategy

Problem Solving strategy Step 5: Determine the current passing through each branch of the parallel set Step 6: Determine the potential drop for the individual resistors when there is a series within the parallel branches Problem Solving strategy

Problem Solving Strategy You now have ALL the boxes filled in Use Kirchhoff’s rules to spot-check your work. Resistor: Resistance /W Potential Drop / V Current / A R1: R2: R3: R4: R5: Problem Solving Strategy