CH01 and 02

Thomas L. FloydElectronics Fundamentals, 6eElectric Circuit Fundamentals, 6e

Copyright 2004 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458

All rights reserved.

Basic Circuit Example

(Load)

All Circuits Require: 1. Voltage Source2. A Load (or it would be a short circuit)3. A Conductive Path




Basic Circuit Schematic

All Circuits Require: 1. Voltage Source2. A Load (or it would be a short circuit)3. A Conductive Path

(Load)

Metric Prefixes

Metric prefixes are symbols that represent the powers of ten used in Engineering notation

Electrical Units




Voltage and Current Flow in a Circuit

No Voltage Applied

Electrons flow from negative to positive when a voltage is applied across a conductive material.




Voltage Applied

Illustration of 1 A of current (1C/s) in a material




Resulting Electron Current Flow (1 Ampere)




A (CM) = d2

American Wire Gage (AWG):Gage Number Up -> Wire Size Down




Wire Gage Measurement

House Wiring and AmperageWire Use Rated Ampacity Wire Gauge

Low-voltage Lighting and Lamp Cords

10 Amps 18 Gauge

Extension Cords 13 Amps 16 Gauge

Light Fixtures, Lamps, Lighting Runs

15 Amps 14 Gauge

Receptacles, 110-volt Air Conditioners, Sump

Pumps, Kitchen Appliances

20 Amps 12 Gauge

Electric Clothes Dryers, 220-volt Window Air Conditioners, Built-in Ovens, Electric Water

Heaters

30 Amps 10 Gauge

Cook Tops 45 Amps 8 Gauge

Electric Furnaces, Large Electric Heaters

60 Amps 6 Gauge

Electric Furnaces, Large Electric Water

Heaters, Sub Panels

80 Amps 4 Gauge

Service Panels, Sub Panels

100 Amps 2 Gauge

Service Entrance 150 Amps 1/0 Gauge

Service Entrance 200 Amps 2/0 Gauge

Printed Circuit Board (PCB)Foil Traces as Conductors

Components are mounted on Opposite Side

Empty Board Showing Traces and Connection Pads Populated Board Showing

Traces and Soldered Connections




Ground is not Always Earth Ground

CommonEarth

Ground is Always a Common 0 Volt Reference

A simple circuit with ground connections




Ground is a common path for current to return to the Voltage Supply is considered to have 0V potentialMost Voltage Measurements are made Referenced to Ground

(Electron Flow)

Sizes of common batteries




Battery Voltage Sources




Battery Voltage Sources

Creates Voltage From Chemical ReactionNo Voltage Source has Unlimited Current Capability

Voltages Add or Subtract Depending Upon Polarity Voltage Stays the Same, but Increased Current Capability




AC Power Supply Voltage Source

Creates DC Voltage From Raw AC Outlet Voltage




Generator/Alternator Voltage Source

Creates Voltage From Rotating Magnetic FieldsRequiring a Great Amount of Force/Torque




Solar Cell Voltage Source

Creates Voltage From Exposure to Light

Fuel Cell Voltage Source

Electronic power supplies. (Copyright Tektronix, Inc. Reproduced by permission.)




Workbench Voltage/Current Power Supplies

Example of a voltmeter connection to measure voltage in a simple circuit




Measuring Voltage

Example of an ammeter connection to measure current in a simple circuit




Measuring Current

Resistance/resistor symbol




Basic Resistor Symbol

Resistors

Two common types of individual fixed resistors with axial leads




Low Watt Axial Lead Resistors

Chip resistor and resistor networks




Low Watt ResistorsSize of Resistor is Based Upon Wattage Rating

Two types of fixed resistors (not to scale)




Low Watt Resistor Construction

The power rating of a resistor is directly related to its surface area and its material




Relative sizes of metal-film resistors with standard power ratings of 1/8 W, 1/4 W, 1/2 W, and 1W




Typical resistors with high power ratings.




Typical wirewound power resistors




Higher Watt Resistors

Common types of power resistors




Higher Watt Resistors

Construction views of typical film resistors




Resistor Construction

High Watt LowWatt

Resistor Color Codes




12K Ohms

Resistor color codes




Answers on Next Slide




100 Ohms 5.6M Ohms27K Ohms

Example of three-digit labeling for a resistor




Other Labeling Method

Example of using an ohmmeter to measure resistance




Measuring Resistance

Potentiometer and rheostat symbols and basic construction of one type of potentiometer




Variable Resistors/Potentiometers/POT

Have Moveable Wiper to Vary ResistanceCan be used as Voltage or Current Dividers

Examples of (a) linear and (b) tapered potentiometers




Type Used in Volume ControlsMost Common Type

More Change at Low VolumeLess Change at High Volume

Typical potentiometers and two construction views




Potentiometer ExamplesSmaller POTS are called Trimmers

Symbols for resistive devices with sensitivities to temperature and light




Both Usually have Negative Coefficients

Temperature UpResistance Down

Light Level UpResistance Down

Special Purpose Resistors

Common Thermistor Use

Modern Thermostats use them to Sense Room Temperature




Special Purpose Resistors

Strain GageAttached to a surface Resistance changes when stretched or bent

Illustration of closed and open circuits using an SPST switch for control




Simple On/Off SwitchOpen or Closes the Circuit

Switches

An example of an SPDT switch controlling two lamps




Switching Between two Circuits

Switches

Switch symbols




Types of Common Switches

Single PoleSingle Throw

Single PoleDouble Throw

Double PoleSingle Throw

Double PoleDouble Throw

Normally-OpenPush Button

Normally-ClosedPush Button

Basic On/Off Switch Switch BetweenTwo Circuits

On/Off Two Circuits

Doorbell Car Open-DoorBeeper

Multi-FunctionControl SwitchOne Source,Two Circuits




SPDT Controlling Two Circuits





Double PoleSingle Throw



Single PoleRotary




Rotary Switch Controlling Four Circuits

Single PoleRotaryMulti-FunctionControl Switch




Good Rotary Switch Application

Multi-FunctionControl Switch

Typical mechanical switches




Construction view of a typical toggle switch




SPDT

Why we Have Circuit Protection

Typical fuses and circuit breakers and their symbols

Circuit ProtectionWire Fast BlowWire Fast BlowWire Fast BlowChemical Slow Blow

Automotive

Household Circuit Breaker

Industrial Fuses

Once a fuse is blown, It cannot be reusedOnce a Circuit Breaker is Tripped, It can be Reset

Household Circuit Breakers220V Line Voltage

Tripped

Breaker PanelThe more current, the more the electromagnet becomes magnetizedAt the specified breaker current, there is enough magnetic force to pull the breaker contact openBreaker is Reset by pushing the switch to Off and then back to On

Neutral

Earth Ground at Bottom of Panel

Set

Household Breaker Panels

Heat from Overloaded Circuits Interleaved Bus Bars

220V Line Voltage Neutral

Bad Connections and Arc Hazard

GFCI receptacleTrips Much Faster Than Circuit

Breaker or Fuse

Compares current between Hot and Neutral and if not equal, Trips (Opens) the circuit

HotNeutral

Ground

FIGURE 2-53 Shock hazard in terms of three basic current path groups.




Shock Hazard

Current Kills:You dont want it to pass through your heart-First and Last Example




Review of Symbols




DC Power SupplyFunction Generator

Digital Multimeter - DMM Oscilloscope OScope

Common Electronic Test Equipment

Documents

CH01 and 02