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1Physics I Honors
Current and Circuits
Circuits
Schematics
Use of Meters
2Physics I Honors
Objectives
• Describe the utilization of ammeters and voltmeters in circuits.
• Describe the utilization of fuses and circuit breakers in protecting electrical circuits
3Physics I Honors
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
4Physics I Honors
Components - SourceDRY CELL
a source of electrical energy
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5Physics I Honors
Components - LoadLIGHT BULBLIGHT BULB
lights up whenlights up whenelectricity pass throughelectricity pass through
6Physics I Honors
Circuit - CompleteSource of electrical energySource of electrical energy
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AppliancesAppliances
Complete circuitComplete circuit
Electricity flowsElectricity flows
7Physics I Honors
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
8Physics I Honors
Schematics
Circuit diagrams, also called schematic diagrams, provide a graphic representation of an electric circuit using standard symbols.
9Physics I Honors
Diagram Symbols
wire or conductor
resistor or other load
bulb voltmeter
battery ammeter
switch generator
V
A
10Physics I Honors
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.
11Physics I Honors
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
12Physics I Honors
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
13Physics I Honors
Example – Simple Circuit
circuit diagramcircuit diagram
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A+ -
A
14Physics I Honors
Complex Circuit
Construct theConstruct thecircuit diagramcircuit diagram
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A
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A