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Electric Circuits. Concept Summary Holloway High School Physics. Circuit Schematics. A schematic diagram is a symbolic representation of a circuit. A symbol represents each item in the circuit Lines represent wires (paths for charges). Circuit Symbols. Three Types of Circuits. Series
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Electric Circuits Concept Summary Holloway High School Physics
Circuit Schematics • A schematic diagram is a symbolic representation of a circuit. • A symbol represents each item in the circuit • Lines represent wires (paths for charges).
Three Types of Circuits • Series • Parallel • Compound
Series Circuits • Series circuits have 1 path for charges to flow.
Series Circuits • Voltage may be different across different objects in a series circuit. • Sum of the individual voltages = source voltage • Current is the same in all parts of a series circuit. • If one “goes out”, they all “go out”
Parallel Circuits • A parallel circuit has two or more paths for charges to move.
Parallel Circuits • Voltage is the same across each element in a parallel circuit. • Current may vary through different elements in a parallel circuit. • Sum of the individual currents = source current. • If one “goes out”, the other “stays lit”.
Compound Circuits • A compound circuit has both series and parallel parts.
Adding Resistance in Series • When you add resistance in series: • Total resistance increases • Current decreases
Equivalent Series Circuits • Rseries = R1 + R2 = 10 Ω + 10 Ω = 10 Ω
Adding Resistance in Parallel • When you add resistance in parallel: • Total resistance decreases • Current increases
Equivalent Parallel Circuits • 1/Rparallel = 1/R1 + 1/R2 • 1/Rparallel = 1/20 Ω + 1/20 Ω = 2/20 Ω • 1/Rparallel =1/10 Ω • Rparallel = 10 Ω
Adding Resistance in Compound Circuits • A compound circuit has both series and parallel parts, but one adds resistances as shown above.
Adding Resistance in Compound Circuits • Rcompound = R1 + R2 + [1/(1/R3 + 1/R4)] • Rc = 10 Ω + 10 Ω + [1/(1/20 Ω +1/20 Ω)] • Rc = 20 Ω + [1(2/20 Ω)] = 20 Ω + 10 Ω • Rc = 30 Ω • Draw the equivalent circuit.
Household Circuits • Household circuits are: • parallel circuits • Typically designed to carry 15 Amperes of current - maximum.
Overloading Circuits • Since adding resistance to a parallel circuit causes current to increase, adding appliances to a household circuit causes current in the house wiring to increase. • This means wires must dissipate more heat energy (P = I2R).
Short Circuits • A short circuit is a very low resistance path in a circuit. • A short circuit will also cause large amounts of current to flow in a circuit and overload the circuit.
Fuses & Circuit Breakers • Fuses & circuit breakers act as automatic switches in a circuit to prevent dangerous currents from flowing.