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20.1 Schematic Diagrams and Circuits p730 - 735. Essential Questions  How does the wiring in a circuit change its ability to supply power to devices?

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Presentation on theme: "20.1 Schematic Diagrams and Circuits p730 - 735. Essential Questions  How does the wiring in a circuit change its ability to supply power to devices?"— Presentation transcript:

1 20.1 Schematic Diagrams and Circuits p

2 Essential Questions  How does the wiring in a circuit change its ability to supply power to devices?  How do we represent physical circuit elements in schematic drawings?

3 Objective(s): We will be able to…  Interpret and construct circuit diagrams.  Identify circuits as open or closed.  Deduce the potential difference across the circuit load, given the potential difference across the battery’s terminals.

4 Agenda:  Warm-Up  Recap what happened on Friday.  Reminder: Chapter 19 Test Tomorrow.  Introduction to Circuit Diagrams  Notes:  Schematic Diagrams  Circuits and short circuits  EMFs

5 Warm Up  The following drawings are used in circuit diagrams. List what you think each object represents. Wire Resistor Light Bulb Plug Battery/D C Source Switch Capacitor

6 Schematic Diagrams  A diagram that is used to represent the construction of an electrical apparatus is a schematic diagram. Sometimes called a circuit diagram.  They are used to determine how parts in an electrical device are arranged, and to help understand how they work.

7 Schematic Diagram Symbols  Wire or conductor

8 Schematic Diagram Symbols  Resistor or circuit load (Overall resistance. Discussed more in a minute.)

9 Schematic Diagram Symbols  Bulb or lamp

10 Schematic Diagram Symbols  Plug

11 Schematic Diagram Symbols  Battery

12 Schematic Diagram Symbols  Switch

13 Schematic Diagram Symbols  Capacitor

14 Electric Circuits  An electric circuit is a pathway through which charges can be conducted.  Circuits (and switches) must be closed to complete the pathway, otherwise charges will not flow. Light switch on.  Open circuits conduct no electricity. Light switch off.

15 Electrical Circuits  All circuits consist of two things…  A source of potential difference (electrical energy), like a battery, and…  A load: an element or group of elements in a circuit that dissipates energy.

16 Light Bulbs  Light bulbs themselves are a complete circuit with a resistor.  The filament acts as a resistor, converting electrical energy into internal energy and thus heat and light.

17 Short Circuits  Without a load (bulb or resistor), a circuit has very little resistance.  And therefore, very high current.  This is called a short circuit.  Most wires overheat when they short circuit (think of the battery and the paperclip). DANGEROUS!  This is why we have fuses and circuit breakers.

18 Electromotive Force (emf)  Literally, the force that moves electrons.  Any device that increases the flow of charge in a circuit is a source of emf, the energy per unit charge supplied by the source.  In real life, the terminal voltage (actual potential difference from the battery) is less than its emf due to internal resistance.  The amount of power the battery actually supplies is less than what it should, because some of the energy is wasted internally.

19 Terminal Voltage  The potential difference across a load equals the terminal voltage.  Meaning: if a battery supplies 1.5 volts of potential difference,  then the voltage across the resistor, bulb, or collection of resistors and bulbs etc. is 1.5 volts.  No energy created or destroyed.

20 Recap  Circuit diagrams are used to represent and analyze the composition of electric devices.  Open circuits do not have a complete pathway, so they do not conduct electricity. Closed circuits complete the pathway, so they do conduct electricity.  The voltage across the load of a circuit is the same as the voltage supplied by the battery.

21 Homework  Tonight: Finish study guide.  Due Wed: p 735 #1-5


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