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DAY1 BASIC ELECTRICAL CONCEPTS
CONSTRUCTION 275
ELECTRICAL UNITS AND SYMBOLS
QUANTITY
UNIT
SYMBOL
CURRENT
AMPERE(A)
I
VOLTAGE
VOLT(V)
V
RESISTANCE
OHM(Ω)
R
FREQUENCY
HERTZ(Hz)
f
WATTS(W)
P
POWER
ELECTRICAL QUANTITIES AND UNITS
COULOMB: BASE UNIT OF CHARGE=
CHARGE SYMBOL =Q
ABBREVIATION
=C
6.25 1018 ELECTRONS
CURRENT= Q/t CHARGE/TIME
1A  1C s
AMPERE

ONE COULOMB/SEC OR
6.25 1018
ELECTRONS/ SEC
-
ELECTRIC CURRENT (I): MOVEMENT OF CHARGED PARTICLES IN A SPECIFY DIRECTION CAN BE +OR .
Basic Electricity - What is an amp?
http://www.youtube.com/watch?v=8gvJzrjwjds
Copper: The Miracle Metal
http://www.youtube.com/watch?v=sSVI5l-MbMQ&list=UU2bkHVIDjXS7sgrgjFtzOXQ
CURRENT THAT IS FLOWING IN THE SAME DIRECTION ALL
THE TIME IS KNOWN AS DIRECT CURRENT
SYMBOL I WAS CHOSEN FOR CURRENT BECAUSE IT WAS THOUGH TO
REPRESENT THE INTENSITY OF ELECTRICITY IN A WIRE. CURRENT MOVES AT
LESS THAN THE SPEED OF LIGHT IN ANY WIRE.
VOLTAGE=EMF(ELCTROMOTIVE FORCE)=POTENTIAL DIFFERENCE
UNIT OF VOLTAGE (V) IS THE VOLT.
POLARITY: HELPS TO INDICATE WHICH
DIRECTION CURRENT IS FLOWING.
CAN BE + OR -
WHEN TERMINALS ARE IDENTIFIED ON A ELECTRONIC DEVICE, IT IS SAID
TO BE POLARIZED.
POLARITY MUST BE CORRECT FOR THE DEVICE TO WORK. IF THE DEVICE IS
CONNECTED BACKWARD, IT IS SAID TO BE IN A STATE OF REVERSE POLARITY
AND NO CURRENT WILL FLOW.
REMEMBER ONE FORM OF ENERGY MUST BE CONVERTED
FROM ONE FORM TO ANOTHER TO CREATE
VOLTAGE.EXAMPLES:POWER PLANT GENERATORS
COAL
GEOTHERMAL
SOURCES OF VOLTAGE
CONVERT MECHANICAL
ENERGY INTO
ELECTRICAL ENERGY
NUCLEAR
SOLAR
HYDROELECTRIC
RESISTANCE:OPPOSITION TO CURRENT FLOW IN A MATERIAL.
ELECTRICAL ENERGY IS CONVERTED INTO HEAT.
CONDUCTORS: OFFER LITTLE RESISTANCE TO CURRENT FLOW. WHY? DO
TO THE EASE AS WHICH VALANCE ELECTRONS CAN BE RELEASED FROM
THE OUTER SHELL OF AN ATOM.
GOOD CONDUCTORS: SILVER,GOLD,ALUMINUM,COPPER.
BAD CONDUCTORS: RUBBER,WOOD,CERAMIC MATERIAL, GLASS
INSULATORS HAVE HIGH RESISTANCE TO CURRENT FLOW.
A BAD CONDUCTOR IS A GOOD INSULATOR.
MOST INSULATORS ARE COMPOUNDS OF TWO OR MORE ELEMENTS. THEY SHARE
ELECTRONS BY COVALENT BONDING.(MAKES IT HARDER FOR ELECTRONS TO BE
FREED.) LIKE THESE GLASS AND CERAMIC INSULATORS.
UNIT OF RESISTANCE THE OHM. Ω
4 FACTORS THAT EFFECT RESISTANCE
1. TYPE OF MATERIAL
2. LENGTH OF OBJECT
3. CROSS SECTIONAL AREA
4. TEMPERATURE OF OBJECT
Make presents ohm’s law
http://blog.makezine.com/2009/12/23/make-presents-ohms-law/
POWER/ENERGY: ABILITY TO DO WORK, GAUGE OF HOW ENERGY IS CONVERTED
FROM ONE FORM TO ANOTHER.
POWER CAN ALSO BE THOUGHT OF AS THE RATE OF USING ENERGY OR WORK.
EFFICIENCY 
Poweroutput
Powerinput
x100%
Eout
EFFICIENCY 
x100
Ein
FOR 100%EFFICIENCY, Pout =Pin,
NOT POSSIBLE!!
VIOLATES THE LAWS OF THEMODYNAMICS
SIX PARTS OF AN ELECTRIC CIRCUIT
1.ENERGY SOURCE: VOLTAGE SOURCE: TO CREATE ELECTRIC FIELD WHICH STARTS CURRENT FLOW
2.CONDUCTORS:
PATHWAY FOR CURRENT TO FLOW.
3.INSULATORS:
PREVENTS CURRENT FROM GOING WHERE WE DON’T WANT IT TO.
4.LOAD :
PLACE WHERE CURRENT CAN BE CONTROLLED AND CONVERTED
FOR ITS INTENDED USE.
5.CONTROL DEVICE:SWITCH TO TURN THE CURRENT ON/OFF.
6.PROTECTION DEVICE: STOPS CURRENT FLOW IF OVERLOAD OCCURS(USUALLY A SHORT CIRCUIT.)
FIRST 4 PARTS ARE ESSENTIAL, LAST 2 ARE OPTIONAL.
EXAMPLE OF A SIMPLE CIRCUIT, FLASHLIGHT
HAS LOAD,VOLTAGE SOURCE, AND CONTROL DEVICE.
FLASHLIGHT CASE IS PART OF THE CONDUCTIVE PATH.
ARROWHEAD INDICATES DIRECTION OF CURRENT FLOW.
MEASURING ELECTRICAL QUANTITIES
•
•
•
•
VOLTAGE:
VOLTMETER
CURRENT:
AMMETER
RESISTANCE: OHMMETER
POWER:
WATTMETER
MULTIMETER:COMBO OF VOLTMETER,AMPMETER AND OHMMETER.
TWO TYPES, DIGITAL AND ANALOG
Make Magazine: the multimeter
http://www.youtube.com/watch?v=BW3Wj7UD-_s
ANALOG MULTIMETER:VOM
(VOLT-OHM- MILLIAMETER)
•
•
•
HAVE FUNCTIONS:WHAT QUANTITY IS BEING MEASURED.
HAVE RANGES: AMOUNT OF QUANTITY BEING MEASURED.
HAVE SCALES: DEPENDS ON FUNCTION AND RANGE THAT METER IS SET TO.
VOM HAVE 5 FUNCTIONS.
1 AC VOLTAGE
2 DC VOLTAGE
3 DC CURRENT
4 RESISTANCE
5 CONTINUITY
OHM SCALE: DIFFERENT FROM OTHER SCALES
1.
REVERSE READING
2.
NONLINEAR
3.
DIVISON OF SCALES IS NONLINEAR.
DIGITAL MULTIMETERS NO SCALES,BETTER ONES HAVE AUTORANGING
TESTING CONTINUITY
MEASURING RESISTANCE
ON VOM:TOUCH TEST LEADS TOGETHER,USE ZERO OHM KNOB TO SET TO
ZERO, MUST BE REPEATED FOR EACH SCALE.
THE OHMMETER FUNCTION HAS ITS OWN POWER SOURCE
(INTERNAL BATTERY) TO ALLOW RESISTANCE MEASUREMENTS.
DON’T TOUCH METAL PARTS OF TEST LEADS WHEN MAKING MEASURMENTS.
MEASURING VOLTAGE: POWER IS CONNECTED TO THE CIRCUIT.
MEASURING CURRENT: MUST INSERT METER INTO CIRCUIT PATH TO WORK
AMMETER CAN BE DAMAGED IF USED INNCORRECTLY.(LIKE A VOLTAGE METER)
MEASURING VOLTAGE: POWER IS CONNECTED TO THE CIRCUIT.
MEASURING VOLTAGE ACROSS LAMP2.
MEASURING CURRENT: MUST INSERT METER INTO CIRCUIT PATH TO WORK
AMMETER CAN BE DAMAGED IF USED INNCORRECTLY.(AGAIN IF USED LIKE A VOLTAGE METER)
WIRE,CABLES
WIRE IS A SINGLE CONDUCTOR (INSULATED OR NON INSULATED)
CABLE HAS MULTIPLE CONDUCTORS
CONDUCTORS CAN BE SOLID OR STRANDED
SOLID COPPER
CONDUCTOR COVERED
WITH INSULATION
Increasing gauge numbers give decreasing wire diameters, This gauge system
originated in the number of drawing operations used to produce a given gauge of
wire. Very fine wire (for example, 30 gauge) required more passes through the
drawing dies than did 0 gauge wire.
The AWG tables are for a single, solid, round conductor. The AWG of a stranded
wire is determined by the total cross-sectional area of the conductor, which
determines its current-carrying capacity and electrical resistance. Because there
are also small gaps between the strands, a stranded wire will always have a
slightly larger overall diameter than a solid wire with the same AWG.
AWG gauges are also used to describe stranded wire. In this case, it describes a
wire which is equal in cross-sectional area to the total of all the cross-sectional
areas of the individual strands; the gaps between strands are not counted. When
made with circular strands these gaps occupy about 10% of the wire area, thus
requiring a wire about 5% thicker than equivalent solid wire.
Stranded wires are specified with three numbers, the overall AWG size, the
number of strands, and the AWG size of a strand. The number of strands and the
AWG of a strand are separated by a slash. For example, a 22 AWG 7/30 stranded
wire is a 22 AWG wire made from seven strands of 30 AWG wire.
STRANDED CONDUCTORS
MANY WIRES TWISTED TOGETHER, MORE FLEXIBLE THEN SOLID WIRE.
SMALLER WIRES ARE OFTEN COATED WITH A THIN LAYER OR SOLDER,
SINCE BARE COPPER OXIDIZES EASILY.
YOU TUBE: Cable Basics 101: Conductors
http://www.youtube.com/watch?v=gtAaZ2hFYTA
MULTIPLE LOAD CIRCUITS
IF YOU HAVE TWO OR MORE LOADS, THEY CAN BE CONSTRUCTED IN
SERIES, PARALLEL OR SERIES-PARALLEL.
SERIES CIRCUITS: ONE PATH FOR CIRCUIT FLOW.
-
R1
+
-
-
R2
VT
+
IT
+
+
R3
CURRENT IS THE SAME IN EACH ELEMENT: IT=I1=I2=I3
IN SERIES CIRCUITS CURRENT IS THE SAME IN EACH ELEMENT.
SO
IT  I1  I 2  I 3
AN AMPERE METER PLACED AT ANY POINT IN THE CIRCUIT WILL GIVE THE SAME CURRENT READING.
RESISTANCE IN A SERIES CIRCUIT, ADD TOGETHER FOR THE TOTAL RESISTANCE.
RT  R1  R2  R3  ....RN
VOLTAGE IN SERIES CIRCUITS
VOLTAGE IS DIVIDED UP ACROSS EACH LOAD.
VT  V1  V2  V3
10V
R1
30V
R2 10V
VT
IT
R3
10V
FINDING A OPEN IN A SERIES CIRCUITS
IF ANY PART OF THE CIRCUIT IS OPEN,CURRENT
STOPS,VOLTAGE,POWER ARE REMOVED FROM ALL THE
LOADS.
0V
V
R1
12 V
R2
R3
V
0V
V
0V
FINDING SHORTS IN SERIES CIRCUITS: WHEN ONE LOAD
IS SHORTED OUT, OTHERS MAY CONTINUE TO OPERATE.
10V,10W
1A
L1
15V,25W
L2
30V
10V,10W
1.5A
L1
SHORT
L3
L2
30V
10V,10W
L3
IN THIS EXAMPLE WHEN L2 IS SHORTED, THE OTHER LAMPS
CURRENT AND VOLTAGE INCREASE 50%. THE INCREASED
POWERTO THE LAMPS WILL LIKELY BURN THEM OUT.
15V,25W
0V,0W
PARALLEL CIRCUITS
IS A MULTILOAD CIRCUIT WITH MORE THEN ONE CURRENT PATH. EACH PATH IS
CALLED A BRANCH.
EACH BRANCH HAS ITS OWN LOAD. TOTAL CURRENT IS SPLIT ACROSS EACH
BRANCH. EACH BRANCH IS INDEPENDENT OF THE OTHERS.
IT
I1
V
I2
R1
I3
R2
R3
IF A BREAK IN CURRENT FLOW
OCCURS IN A SERIES CIRCUIT
LIGHTS GO OUT!
IN A PARALLEL CIRCUIT, IF ONE BRANCH
IS CUT OFF.THE OTHER BRANCH STILL
WORKS AND THE LAMP GLOWS.
SERIES-PARALLEL CIRCUIT
ELECTROMAGNETISM
A MOVING ELECTRIC CURRENT CREATES A MAGNETIC
FIELD WHICH IS PERPENDICULAR TO THE CURRENT
FLOW.
Field strength is directly proportional to the amount of current flowing
thru the conductor. If the current doubles, the field strength doubles.
FORCE BETWEEN CONDUCTORS
TWO PARALLEL CURENT CONDUCTOTS ATTRACH EACH OTHER IF THE
CURRENTS ARE FLOWING IN THE SAME DIRECTION. THERE FIELD LINES JOIN
TOGETHER. THE OPPOSITE OCCURS IF CURRENTS ARE TRAVELING IN THE
OPPOSITE DIRECTION
X
X
ATTRACH EACH OTHER
REPEL EACH OTHER
X
MAGNETISM
MAGNETISM IS A FORCE THAT ACTS ON CERTAIN MATERIALS.
WHAT MATERIALS? ALLOYS OF COPPER,NICKEL ALUMINIUM, IRON, COBALT.
THIS MAGNETIC FORCE IS REFERRED TO AS A MAGNETIC FIELD. THE FIELD
EXTENDS OUT FROM THE MAGNETIC MATERIAL IN ALL DIRECTIONS.
LINES OF FORCE OF A MAGNETIC FIELD ARE KNOW AS MAGNETIC FLUX (Φ)
FLUX IS STRONGER WHERE LINES OF FORCE ARE CLOSER.
FLUX IS WEAKER WHERE LINES OF FORCE ARE FATHER APART.
FLUX IS ALWAYS STRONGEST AT THE END OF A MAGNET.
LINES OF FORCE LEAVE THE N POLE AND ENTER THE S POLE.
AS WITH ELECTRIC CHARGES, LIKE MAGNETIC POLES REPEL
EACH OTHER, UNLIKE MAGNETIC POLES ATTRACT EACH OTHER.
COILS
IF A CURRENT CARRYING WIRE IS TIGHTLY WOUND
INTO A COIL, A ELECTROMAGNET IS CREATED.
SIMPLE TRANFORMER
WHEN A CURENT CARRYING WIRE IS WRAPED AROUND A IRON CORE
( PRIMARY WINDING) IT WILL INDUCE A MAGNETIC FLUX IN THE IRON CORE.
IF A SEPARATE SECOND COIL IS WRAPED AROUND THE CORE(SECONDARY WINDING) A
CURRENT WILL BE INDUCED IN THIS WIRE.
STEP UP/DOWN TRANSFORMERS
SOLENOIDS
AN ELECTROMAGNETIC DEVICE THAT ALLOWS A ELECTRIC
CIRCUIT TO CONTROL A MECHANCIAL DEVICE.( VIA A PLUNGER)
HOW DOOR CHIMES WORK
RELAYS
A relay is an electrical switch that can be opened or closed by an electrical
signal. It is an electrically controlled switch.
People use them when they want a small amount of electricity to control a
bigger amount of electricity.
The same thing can be done with transistors, but transistors can't handle
the amount of current that relays can.
AC AND VOLTAGE
FOR A DC WAVEFORM IN A SIMPLE CIRCUIT THE OUPUT IS ALWAYS CONSTANT, EXCEPT WHEN
THE CIRCUIT IS SWITCHED ON/OFF. DC WAVE FORMS CAN BE + OR - BUT NEVER BOTH.
CYCLE : ONE WAVEFORM THAT DOES NOT REPEAT ITSELF.
½ CYCLE
.25 S
PERIOD (T) : TIME TO COMPLETE ONE CYCLE.( IN THIS CASE .25 SECONDS).
FREQUENCY( f ) : # OF CYCLES/SECOND
Time (sec) FOR THIS WAVEFORM f = 1 CYCLES/SEC
HERTZ: UNIT OF FREQUENCY . FOR THE ABOVE WAVEFORM f = 1 Hz
AMPLITUDE: HEIGHT OF THE
WAVEFORM.
RMS value is an equivalent DC value which tells you how many volts or
amps of DC that a time-varying sinusoidal waveform is equal to in terms
of its ability to produce the same power. For example, If you have mains
supply of 240Vac and is assumed an effective value of “240 Volts RMS”.
This means then that the sinusoidal RMS voltage from the wall sockets of
a home is capable of producing the same average positive power as 240
volts of steady DC voltage as shown below.
ADVANTAGES OF A.C. OVER D.C. / WHY GENERATION IS DONE IN A.C.
1. AC CAN BE GENERATED AT HIGH VOLTAGES.
2. HV AC GENERATORS ARE SIMPLER AND CHEAPER THEN DC
GENERATORS.
3. AC CAN BE STEPPED UP OR DOWN WITH TRANSFORMERS.
ACTUAL VOLTAGES COULD BE MEASURED AS 110V,115, 118V,125V, ETC.
NOMINAL VOLTAGE MEANS IN NAME ONLY, NOT A FACT.( USE OF 120V)
ADVANTAGES OF HIGH VOLTAGE TRANSMISSION LINES
STEP UP TRANSFORMER
AT POWER PLANT
20KV
500A
10 MW
400KV
25A
10 MW
LONG DISTANCE
TRANSMISSION LINES
STEP DOWN DISTRIBUTION
TRANSFORMER AT SUBSTATION
400KV
25A
20KV
500A
10 MW
TO LOADS AND OTHER
STEP DOWN
TRANSFORMERS.
50Hz vs. 60Hz
UTILITY FREQUENCIES IN USE IN 1897 IN NORTH AMERICA
Hz
Description
140
Wood arc-lighting dynamo
133
Stanley-Kelly Company
125
General Electric single-phase
66.7
Stanley-Kelly company
62.5
General Electric "monocyclic"
60
Many manufacturers, becoming "increasingly
common" in 1897
58.3
General Electric Lachine Rapids
40
General Electric
33
General Electric at Portland Oregon for rotary
converters
27
Crocker-Wheeler for calcium carbide furnaces
25
Westinghouse Niagara Falls 2-phase - for
operating motors
3 PHASE AC:
POWER PLANTS PRODUCE 3 PHASE AC. EACH PHASE IS SEPARATED BY 120°.
3 PHASES ARE CONNECTED SO THE LOAD CAN BE CARRIED ON 3
CONDUCTORS FROM THE POWER PLANT TO THE USER.
3 PHASES ARE CONNECTED IN EITHER DELTA OR WYE CONFIGURATION.
3 PHASE 120 V/208V 4 WIRE WYE SYSTEM
LINE 1
120 V
PHASE 1
120 V
208 V
NEUTRAL
PHASE 3
120 V
PHASE 2
120 V
120 V
TO 3 PHASE
LOADS
208 V
LINE 2
GROUND
120 V
208 V
LINE 3
UNDER LOAD:LINE AND PHASE CURRENTS ARE NOT EQUAL.
SINCE 2 PHASE VOLTAGES ARE SEPARATED BY 120º , THEY CANNOT BE ADDED TOGETHER
ILINE = 1.732IPHASE
VLINE = 1.732VPHASE
VLINE2 = 1.732(120V) = 208V
SINGLE PHASE 120 V ARE CONNECTED BETWEEN THE NEUTRAL AND ANY LINE.
SINGLE PHASE 208 V CIRCUITS ARE CONNECTED BETWEEN ANY 2 OF THE 3 LINES.
3 PHASE 208 V ARE CONNECTED ACROSS 3LINES.
BATTERIES,CELLS ARE POWER SOURCES.
CELLS:
MADE FROM TWO ELECTRODES,TWO DIFFERENT METALS AND
A ELECTROLYTE. CHEMICIAL REACTION BETWEEN THE 3
PRODUCE ELECTRIC.
BATTERY: TWO OR MORE CELLS.
CELL
BATTERY
TWO TYPES OF CELLS
PRIMARY: NOT RECHARGABLE
SECONDARY :RECHARGABLE, # OF CYCLES VARIES FROM 100’S TO1000’S.
WET CELL: USED IN UPRIGHT POSITION TO PREVENT ELECTROLYTE LEAKAGE.
MUST BE VENTED, FOR OUTGASING.
DRY CELL: OPERATE IN ANY POSITION WITHOUT LEAKAGE.
BATTERY CELL RATINGS:AMOUNT OF ENERGY CELL CAN PROVIDE UNDER
CERTAIN CONDITIONS.
DEPENDS ON: TEMPERATURE,CURRENT DRAIN,
DISCHARGE RATE.
CELL/BATTERY CAPACITY IS EXPRESSED IN AMPERE-HOURS (Ah)
LEAD ACID CELL: PRODUCE ABOUT 2.1V/CELL. 12V CAR BATTERY WITH 6
CELLS PRODUCES 12.6 V. WHEN STARTING A CAR 12.6V DROPS TO ABOUT
8V,WHY? AS V DECREASES, INTERNAL RESISTANCE INCREASES PRODUCING
IR VOLTAGE DROP.
BATTERY IS DISCHARGING
BATTERIES
BATTERY IS CHARGING
+
‫־‬
‫־‬
DIRECTION OF ELECTRON FLOW
+
ELCTRON FLOW IS REVERSED
THERE IS A POTENTIAL ENERGY DIFFERENT BETWEEN
THE + AND – TERMINALS OF THE BATTERY. WHEN
CURRENT FLOWS WORK IS DONE. POTENTIAL ENERGY .
IS CONVERTED INTO ANOTHER FORM OF ENERGY, IN THIS
CASE AS HEAT IN THE RESISTOR.
RECHARGING
LEAD-ACID BATTERIES ARE RECHARGED BY FORCING A REVERSE CURRENT
(AT A HIGHER VOLTAGE THEN THE BATTERY RATING) THRU THE CELL.
SPECIFIC GRAVITY: RATIO OF THE WEIGHT OF A
SUBSTANCE TO THAT OF WATER.
EXAMPLE: S.G. OF 1.251 IS 1.251 TIMES HEAVIER THEN WATER.
S.G. INDICATES THE STATE OF CHARGE OF THE BATTERY.
HYDROMETER: USED TO
MEASURE THE S. G. OF A
LEAD-ACID BATTERY.
FULL CELLS
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a
chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common
fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used.
Fuel cells are different from batteries in that they require a constant source of fuel and
oxygen/air to sustain the chemical reaction, they can however produce electricity
continually for as long as these inputs are supplied.
MAN PORTABLE FUEL CELL
The portable JENNY 600S provides power directly to electrical devices or recharges secondary
batteries. The small fuel cartridges contain 0.35l of methanol with a charging capacity of 400Wh
each, equaling 2.2 BA-5590 batteries and saving you up to 80% weight.
SOLDERING
30 WATT SOLDERING IRON
80 WATT SOLDERING STATION
300 WATT SOLDERING IRON
60% TIN/40% LEAD
KESTER 44 SOLDER
WIRES STRIPED
WIRES TWISTED TOGETHER
WESTERN ELECTRIC WIRE SPLICE
TINNING IRON
REMOVING EXCESS SOLDER
HEATING WIRE PRIOR TO SOLDERING
SOLDERING TWISTED PAIR WIRE
FINISHING THE JOB WITH HEATSHRINK TUBING
JOB#12
Knob and Tube - early electrical
insulation
http://www.youtube.com/watch?v=x8ekf
xijhuA&list=UUOc3q8ChcDYyeyFROxL
Dhuw