BASIC ELECTRICAL THEORY

TYPES OF ELECTRICTY

Earth

Cloud High Voltage, Low Current

No Reliable Method to store Electricity

Battery

Low Voltage High Current Local Use only will not work over long Distance

STATIC

+ -

Direct Current DC

Alternating Current AC

Generator

High Voltage, Medium Voltage ,Low Voltage

Wide Current Range + Long Distance

Nuclear Steam /Coal Diesel Engine

Lightning

(Voltage Drops too high for use, caused by cable resistance )

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Nylon Carpet

Voltage Path

High

Low

BASIC ELECTRICAL THEORY

Copper Wire Copper Atoms With Electrons in Orbit

VOLTAGE SOURCE + -

Copper Atom Electron in Orbit Around Atom

Atomic Structure

Electrons forced to next Atom by Voltage pressure, Atom with two electrons Not possible ,atom pushes extra electron to next Atom this process continues As long as Voltage is present this movement is called Electric Current ,and is Measured in Amps

Copper Wire

Voltage and Current

Electron Flow (Current )

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BASIC ELECTRICAL THEORY

Copper Atom Electron in Orbit Around Atom

Atomic Structure Resistance

VOLTAGE SOURCE + -

Copper Wire Electron Flow (Current )

Very Good Conductor (Electrons move easily in copper )

VOLTAGE SOURCE + -

Wood ,Glass, Ceramics

Low Resistance

(ohms)

Very High Resistance

Very Bad Conductor (Electrons very hard to move ) ( Would require Millions of Volts and possible destruction of material )

“Conductor”

“Insulator”

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Current Flow in Simple DC Circuits

+

_

High

Low

+ _

Current flow

High

Low

_

Light Off

Current flow

Light On

+

_ Current flow

+

+

Light Off

Current flow _

Light On

+ Current flow _

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Current Flow in Simple DC Circuits

+ _

+ _ Current flow “Short Circuit “

( Very Dangerous allows very high current to flow, can damage equipment and cause a fire)

+ _ Current flow Light On

( Circuit must have a “Load” connected ie a device to be powered by circuit )

SAFETY FIRST

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BASIC ELECTRICAL THEORY

ELECTROMAGNETISM

Magnetic Field

Cable

AC Voltage Input

+ -

Magnetic Field

Cable

DC Voltage Input

Cable

AC Voltage Output

N

S

N

Moving Permanent Magnet

AC Generator

N

S

N

Spinning Coil

Fixed Permanent Magnet

AC Voltage Output

Steam Turbine Heat Source

Coal, Oil, Gas,Nuclear

Practical AC Generator (Rotor)

(Stator)

Magnetic Effects

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BASIC GENERATORS AC Output

Drilling Machine

Typical Science Project

Magnet

50 Pulses per Second 50 HZ (Hertz)

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“Prime Mover”

BASIC ELECTRICAL THEORY

ELECTROMAGNETIC DEVICES & MACHINES

TRANSFORMERS

AC Voltage Input

AC Voltage Output

Primary Coil Secondary Coil

Magnetic Field

Types – STEP DOWN High Voltage input Low voltage Output

Types – STEP UP Low Voltage input High voltage Output

Soft Iron Core Made up with Thin Plates Stacked Together

Practical Transformer Construction

Primary Coil Secondary Coil

Magnetic Field

Iron Core Concentrates magnetic field

The Number of Turns & The Size of Wire Is how the Voltage & Current Required is Calculated

No Physical Connection Between Coils

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Normally Open ( NO )

Normally Closed ( NC )

Single Pole Change Over (SPCO or CO )

Double Pole Change Over (DPCO)

Crossover Switch

Normally Open Push Button

Normally Closed Push Button

Contact

Contact

c

c

c NO

NC

3

4 2

Crossover Switch Position A

Position B 1

1

2

3

4 Also called “Intermediate” switch

Also called “Intermediate” switch

Exit Push Button

Break Glass Unit

Controller Outputs

BASIC ELECTRICAL THEORY

CONTACTS & SWITCHES

BASIC ELECTRICAL THEORY

ELECTROMAGNETIC DEVICES & MACHINES

RELAYS

C NO NC Coil Coil

v Relay Control Voltage

AC,DC Any Voltage (Chose Specific Relay for application ie 12v dc for Cars )

Common Normally Open

Normally Closed

Control Contact Control

Contact Control Contact

Contacts

Wiring Terminals

Example Shows :- Single Pole Relay

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Current Flow in Simple DC Circuits

_ +

Relay (off )

Current flow

_ +

Relay ( on, energized ) Button Pushed

Current flow

_ +

Button Pushed

Current flow

Led

9V Battery

+

-

12 v

Practical Circuit To Build

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BASIC ELECTRICAL THEORY

C NO NC Coil Coil

Contacts

Parking Boom (22O Volt Motor) Relay Application

+ -

12 v DC Coil

12 v Battery

220 v Socket

Button Open

Relay De Energized Boom Down

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Boom Control Push Button

BASIC ELECTRICAL THEORY

NO NC Coil

Coil

Contacts

Parking Boom (22O Volt Motor) Relay Application

+ -

12 v DC Coil

12 v Battery

220 v Socket

Boom Up Relay Energized Button Closed

Button Closed (Pushed)

Relay Energized Boom Open

C Coil

Boom Control Push Button

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Ground (Earth )

Power Station

BASIC ELECTRICAL THEORY

EARTHING

Live Neutral Earth

(Brown)

(Blue)

(Green/Yellow) x

Cabinet

Live cable Touches Cabinet !

Not Connected

Voltage Runs Through man to Earth Seriously Hurt and or Killed !!

Earth Symbol

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Ground (Earth )

Power Station

BASIC ELECTRICAL THEORY

EARTHING

Live Neutral Earth

(Brown)

(Blue)

(Green/Yellow)

Cabinet

Live cable Touches Cabinet !

Earth Symbol

Earth Connected !

Voltage to earth Via Earth Cable

Fuse Blows/ Circuit Trips Man Safe

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THE DISPLAY (Shows Result of Measurement )

THE SELECTOR SWITCH ( “What do I want to Measure ?” )

Test Cable Input Sockets ( Connects to the object being measured )

Example Measure the Voltage of a DC Battery

Reads 8.754 volts DC

“Battery is slightly Discharged should Be 9 volts dc “

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Selector Switch to DC Volts

THE MULTIMETER DC VOLTAGE

V

THE DISPLAY (Shows Result of Measurement )

THE SELECTOR SWITCH ( “What do I want to Measure ?” )

Test Cable Input Sockets ( Connects to the object being measured )

Example Measure A Short Circuit

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Selector Switch to OHMS (200)

00.1

Touch Probe Tips Together

Displays 0.1 Ohms ie Resistance of Meter Leads

THE MULTIMETER RESISTANCE

Leads Apart (Open Circuit )

THE DISPLAY (Shows Result of Measurement )

THE SELECTOR SWITCH ( “What do I want to Measure ?” )

Test Cable Input Sockets ( Connects to the object being measured )

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Selector Switch to Volts AC

220.0

Electrical Outlet

Warning !! Leads Live to 220 Volts. Do not Touch Any bare metal Parts. Do not short Leads when connected to Socket

The Voltage Levels Present are LETHAL

THE MULTIMETER AC VOLTAGE

THE DISPLAY (Shows Result of Measurement )

THE SELECTOR SWITCH ( “What do I want to Measure ?” )

Test Cable Input Sockets ( Connects to the object being measured )

Example set meter to test continuity

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Selector Switch to

.000

Touch Probe Tips Together

Displays 0 Ohms Ie short circuit & buzzer

THE MULTIMETER CONTINUITY

Leads Apart (Open Circuit )

1.

(diode test/buzzer)

Batteries in SERIES Batteries in PARALLEL

Symbol

Physical Example Typical Circuits

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12v 12v

24v

12v

12v 12v

Double the Voltage Double the Current

12v

Sealed Lead Acid Type

- +