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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