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Chapter 8

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Chapter 8

Combination Circuits (Series-Parallel)

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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Objectives

- Determine the wattage values in a combination circuit.
- Apply combination circuit theory to troubleshoot a combination circuit.

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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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Reducing: Example One

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Reducing: Example One (Cont.)

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Reducing: Example One (Cont.)

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Reducing: Example Two

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Reducing: Example Two (Cont.)

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Reducing: Example Two (Cont.)

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Reducing to a Simple Parallel Circuit

- Solve for total resistance

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Review

What is equivalent resistance of a circuit?

Total resistance of a series-parallel circuit

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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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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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Solving: Example One

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Solving: Example One (Cont.)

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Solving: Example One (Cont.)

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Solving: Example Two

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Solving: Example Two (Cont.)

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Solving: Example Two (Cont.)

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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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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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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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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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Troubleshooting a Combination Circuit (Cont.)

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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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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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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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