1Physics I Honors

Current and Circuits

Circuits

Schematics

Use of Meters

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Objectives

• Describe the utilization of ammeters and voltmeters in circuits.

• Describe the utilization of fuses and circuit breakers in protecting electrical circuits

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Circuit Defined

• A circuit is a path for electrons to flow through. The path is from a power source’s negative terminal, through the various components and on to the positive terminal– Types

• Series

• Parallel

• Combination

                                       

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Components - SourceDRY CELL

a source of electrical energy

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Components - LoadLIGHT BULBLIGHT BULB

lights up whenlights up whenelectricity pass throughelectricity pass through

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Circuit - CompleteSource of electrical energySource of electrical energy

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AppliancesAppliances

Complete circuitComplete circuit

Electricity flowsElectricity flows

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Terms to Know

• Open circuit – there is a break somewhere and electricity cannot flow (maybe the switch is open)

• Closed circuit – electricity can flow (the switch is closed)

• Short circuit – the electricity completes a circuit without going through the load

• Load – what is using the electricity

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Schematics

Circuit diagrams, also called schematic diagrams, provide a graphic representation of an electric circuit using standard symbols.

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Diagram Symbols

wire or conductor

resistor or other load

bulb voltmeter

battery ammeter

switch generator

V

A

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The Ammeter

• This device measures current.

• It is a Galvanometer wired in parallel to a resister (shunt).

• Ammeters are connected in series to the circuit.

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The Voltmeter• This device measures electric

potential…voltage.

• It is a Galvanometer wired in series with a resistor (a multiplier.)

• Voltmeters are connected in parallel to the load

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Fuses and Shorts

If an electric circuit gets “overloaded” (too much current!) fuses or circuit breakers interrupt the flow of current.

•Too many devices can require more current than the wires can handle -- overheating of wires is a fire hazard !!!

Fuses

Circuit Breaker

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Example – Simple Circuit

circuit diagramcircuit diagram

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-

A+ -

A

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Complex Circuit

Construct theConstruct thecircuit diagramcircuit diagram

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A

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A