1. Combination Circuits (Series-Parallel)
Chapter 8
Combination Circuits (Series-Parallel)

2. Objectives
Determine the equivalent circuit resistance for a given combination circuit.
Determine the voltage drops in a combination circuit.
Determine the current values in a combination circuit.
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3. Objectives Determine the wattage values in a combination circuit.
Apply combination circuit theory to troubleshoot a combination circuit.
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4. Reducing a Complex Circuit
Find equivalent resistance of a circuit
Used to solve series-parallel circuits and combination circuits
Reduce to simple series or parallel circuits
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5. Reducing: Example One © Goodheart-Willcox Co., Inc.
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6. Reducing: Example One (Cont.)
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7. Reducing: Example One (Cont.)
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8. Reducing: Example Two © Goodheart-Willcox Co., Inc.
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9. Reducing: Example Two (Cont.)
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10. Reducing: Example Two (Cont.)
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11. Reducing to a Simple Parallel Circuit
Solve for total resistance
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12. Review What is equivalent resistance of a circuit?
Total resistance of a series-parallel circuit
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13. Review What is a combination circuit?
A series-parallel circuit, having a branch of a parallel circuit with resistors in series
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14. Solving for Voltage and Current Values
Once a circuit has been reduced, voltage and current values found with Ohm’s law
Total values can be found first
The circuit can be separated to find all other values
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15. Solving: Example One © Goodheart-Willcox Co., Inc.
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16. Solving: Example One (Cont.)
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17. Solving: Example One (Cont.)
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18. Solving: Example Two © Goodheart-Willcox Co., Inc.
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19. Solving: Example Two (Cont.)
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20. Solving: Example Two (Cont.)
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21. Power in a Combination Circuit
P = I2R or P = E × I
Total power in a combination circuit is equal to the sum of the individual wattages, regardless of whether they are connected with each other in series or parallel
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22. Review
Why must a combination circuit be reduced before solving for individual current and voltage values?
Total values should be found before proceeding to individual values
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23. Review
What is the relationship between total power and individual wattages in a combination circuit?
Total power equals the sum of individual wattages
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24. Troubleshooting a Combination Circuit
Take voltage readings of individual components
Look for an open or a short circuit condition
Check against calculated expected values
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25. Troubleshooting a Combination Circuit (Cont.)
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26. Review
How should an ohmmeter be connected when troubleshooting a series circuit?
With one end of the resistor disconnected from the circuit
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27. Review
Why should you calculate expected values before using meters to troubleshoot a series-parallel circuit?
Because with one parallel resistor open, there is still a path for the current, and the readings can be misleading
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28. For Discussion Discuss Kirchhoff’s two laws for electrical circuits.
Why does the resistance of a conductor decrease as its cross-sectional area increases?
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29. Glossary Combination circuit Equivalent resistance
A series-parallel circuit.
Equivalent resistance
Total resistance of a series, parallel, or combination circuit.
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30. Glossary Series-parallel circuit
Circuit in which parallel branches are in series with other resistors or parallel branches contain resistors in series.
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