DC Circuits
Combination Circuits Many circuits are composed of pieces that are resistors in series and pieces that are resistors in parallel. These pieces may be reduced to equivalent resistors.
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Here, resistors R2, R3, and R4 are in parallel so they can be replaced by a single, equivalent resistor Req.
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Redrawing a circuit may make it easier to understand.
Now it is clear that these resistors are in series.
What single equivalent resistor REQ replaces this bank of resistors in series?
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Most strings of minature Christmas lights are made of bulbs that are connected in series. But each of those bulbs has a filament connected in parallel to another conductor in a way that this "shunt conductor" becomes part of the circuit only when the filament burns out. (Serway's text has a good, detailed description of this).
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What happens if one of the filaments burns out?
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What happens if one of the bulbs is removed?
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(c) Doug Davis, 2002; all rights reserved