1. Current and Circuits Circuits Schematics Use of Meters

2. Objectives • Describe the utilization of ammeters and voltmeters in circuits. • Describe the utilization of fuses and circuit breakers in protecting electrical circuits

3. 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

4. - + Components - Source DRY CELL a source of electrical energy

5. Components - Load LIGHT BULB lights up when electricity pass through

6. - + Circuit - Complete Source of electrical energy Appliances Complete circuit Electricity flows

7. 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

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

9. Diagram Symbols wire or conductor resistor or other load bulb voltmeter battery ammeter switch generator V A

10. 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.

11. 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

12. Circuit Breaker Fuses Fuses and Shorts • Too many devices can require more current than the wires can handle -- overheating of wires is a fire hazard !!! If an electric circuit gets “overlo aded” (too much current!) fuses or circuit breakers interrupt the flow of current.

13. - + A + - A Example – Simple Circuit circuit diagram

14. - + A + - A Complex Circuit Construct the circuit diagram