"Annenberg Media" "¶" "[DRUMROLL]" "[APPLAUSE]" "I THOUGHT IT WAS TIME THIS CLASS HAD SOME CLASS." "ACTUALLY, THESE DAYS," "SCIENTISTS ARE PRETTY INFORMAL PEOPLE." "IT'S CERTAINLY RARE TO SEE ONE DRESSED LIKE THIS." "BUT IN THE 19th CENTURY," "IT WAS NOT UNCOMMON FOR FORMAL LECTURES" "TO BE GIVEN IN FORMAL ATTIRE." "THERE'S NO PLACE THAT THAT WAS MORE TRUE" "THAN AT THE FAMOUS ROYAL INSTITUTION." "I HAVE A PICTURE THAT WAS MADE" "IN THE MIDDLE OF THE 19th CENTURY." "THIS PARTICULAR PUBLIC LECTURE" "SEEMED WORTH IMMORTALIZING IN A PICTURE" "BECAUSE IT WAS ATTENDED BY THE PRINCE OF WALES." "THE PRINCE OF WALES" "PRESUMABLY IS ONE OF THESE CHAPS IN THE FRONT ROW." "THE REASON THIS LECTURE IS WORTH REMEMBERING TODAY" "IS NOT BECAUSE IT WAS ATTENDED BY THE PRINCE OF WALES." "IT'S BECAUSE THE LECTURER WAS MICHAEL FARADAY." "IN FACT, IT WAS AT A LECTURE JUST LIKE THIS ONE," "NEARLY 200 YEARS AGO," "THAT THE YOUNG MICHAEL FARADAY BECAME SO ENTRANCED WITH SCIENCE" "THAT HE DECIDED TO GIVE UP HIS PROMISING CAREER" "AS AN APPRENTICE BOOKBINDER." "BUT IN THAT SERIES OF LECTURES," "THERE IS ONE MAN" "WHO MADE A LASTING IMPRESSION ON THE ENTIRE TRADITION." "HIS NAME WAS CHARLES WHEATSTONE," "AND HE WAS A KEY FIGURE" "IN WORKING OUT THE NUTS AND BOLTS" "THAT MADE ELECTRICITY PRACTICAL." "THOSE NUTS AND BOLTS ARE OUR SUBJECT FOR TODAY." "THE NUTS AND BOLTS THAT HOLD TOGETHER" "THE COMPLEX MACHINERY OF THE MODERN WORLD" "ARE NO MORE IMPORTANT IN THE HISTORY OF CIVILIZATION" "THAN THE SIMPLE FLOW OF WATER." "LEARNING TO CONTROL AND HARNESS THE FLOW OF WATER" "HAS BEEN A CRITICAL INGREDIENT" "IN THE DEVELOPMENT OF CIVILIZATION." "IT WAS NO ACCIDENT THAT THE EARLIEST CIVILIZATIONS" "DEVELOPED ALONG THE BANKS OF THE GREAT RIVERS," "THE NILE, THE TIGRES, AND EUPHRATES," "THE GREAT WATER CIRCUITS OF NATURE." "IN ORDER TO FLOURISH," "EVERY SOCIETY HAD TO DEVELOP THE MEANS TO MANIPULATE," "CONTROL, AND DISTRIBUTE THE FLOW OF WATER" "FOR IRRIGATION," "FOR THE DRAINING OF SWAMPS," "AND TO NOURISH THE GROWTH OF CITIES." "JUST AS ALL ROADS LED TO ROME," "SO DID AN INGENIOUS NETWORK OF AQUEDUCTS." "THE EMPIRE SURVIVED AS LONG AS IT DID," "TO A LARGE DEGREE," "BECAUSE THE AQUEDUCTS BROUGHT DOWN FRESH WATER" "FROM THE HILLS OF ALBANUS." "IN THEIR TIME," "THOSE COMPLEX CIRCUITS OF PIPES THAT DISTRIBUTED WATER" "TO THE CITY'S BATHS, BUILDINGS, AND FOUNTAINS" "WERE AMAZINGLY SOPHISTICATED." "BUT ONLY IN THE LAST CENTURY" "DID ANOTHER FLOWING TECHNOLOGY BEGIN TO DEVELOP" "ELECTRICITY." "INVENTORS SUCH AS THOMAS EDISON" "FOUND WAYS TO MANIPULATE ELECTRIC CURRENTS" "TO LIGHT LAMPS IN HOUSES" "AND TO CARRY DOTS AND DASHES LONG DISTANCES THROUGH WIRES." "THEY ALSO CREATED WAYS" "TO GENERATE AND DISTRIBUTE ELECTRICITY" "IN EVER MORE COMPLEX GRIDS." "BUT IN THE DAYS SINCE EDISON'S ILLUMINATING STATION" "WAS THE WORLD'S PREMIER POWER PLANT," "ENGINEERS HAVE DEVELOPED MUCH MORE SUBTLE WAYS" "TO USE THE FLOW OF ELECTRICITY." "TODAY, A SINGLE COMPUTER CHIP" "CONTAINS AN ELECTRIC CIRCUIT" "AS COMPLEX AS THE STREET MAP OF AN ENTIRE CITY." "AND IN PRINCIPLE," "THE VERY EXISTENCE OF A MAJOR CITY" "SUCH AS LOS ANGELES" "DEPENDS ON MANY OF THESE CIRCUITS." "L.A. IS, OF COURSE, MORE THAN A FREEWAY." "BUT WITHOUT AN ENGINEERING MIRACLE," "IT WOULD BE NO MORE THAN A DUSTY VILLAGE" "BETWEEN THE DESERT AND THE SEA." "AND THAT MIRACLE IS CALLED THE METROPOLITAN WATER DISTRICT." "WHETHER DESIGNING WATER CIRCUITS OR ELECTRIC CIRCUITS," "IT ALL BOILS DOWN TO CONTROLLING THE FLOW OF CURRENTS." "163,000 CUBIC METERS OF WATER PER HOUR" "FLOW THROUGH THE COLORADO RIVER AQUEDUCT" "TOWARD THE LOS ANGELES BASIN." "1.3 AMPS OF ELECTRIC CURRENT FLOW THROUGH THIS COPPER WIRE." "JUST AS WATER MAKES LIFE POSSIBLE," "THE FLOW OF ELECTRICITY MAKES LIGHT POSSIBLE." "HOW MUCH LIGHT" "DEPENDS ON THE AMOUNT OF CURRENT," "WHICH IS MEASURED IN AMPS." "1 AMP IS 1 COULOMB OF ELECTRIC CHARGE PER SECOND" "FLOWING THROUGH A CIRCUIT." "IN OTHER WORDS," "ELECTRIC CURRENT, I," "IS THE RATE OF FLOW OF ELECTRIC CHARGE, q." "AT ANY INSTANT," "THIS CURRENT IS THE SAME EVERYWHERE ALONG THE WIRE" "BECAUSE ELECTRIC CHARGE, LIKE WATER," "IS NEITHER CREATED NOR DESTROYED ALONG THE WAY." "IT JUST KEEPS FLOWING ALONG." "WHILE RIVERS HAVE FLOWED FOR THOUSANDS OF YEARS," "ELECTRICITY WAS BASICALLY A STATIC FIELD UNTIL 1800." "THAT WAS THE YEAR ALESSANDRO VOLTA CHARGED AHEAD" "AND INVENTED THE BATTERY." "THIS NEW SOURCE OF POWER, CALLED THE VOLTAIC PILE," "MADE A SUSTAINED FLOW OF ELECTRICITY POSSIBLE" "AND OPENED THE FLOODGATES OF PROGRESS." "WITH IT, SIR HUMPHREY DAVY" "SOON EXTRACTED BRILLIANT NEW METALS" "SODIUM AND POTASSIUM" "FROM THE COMMON SALTS SODA AND POTASH." "A FEW YEARS LATER," "HANS CHRISTIAN OERSTED DEFLECTED A MAGNETIC NEEDLE" "WITH NOTHING BUT THE CURRENT FROM A VOLTAIC PILE," "AND SO DISCOVERED ELECTROMAGNETISM." "LATER, IN THE 19th CENTURY," "THOMAS EDISON USED THE CONTINUOUS FLOW" "OF ELECTRIC CURRENT PROVIDED BY A VOLTAIC PILE" "TO DEVELOP THE FIRST ELECTRIC LAMP." "HE ALSO USED THAT CURRENT" "TO PERFECT A DEVICE INVENTED BY OTHERS" "THE TELEGRAPH." "MUCH EARLIER, KARL FRIEDRICH GAUSS" "HAD SEEN THE POTENTIAL" "IN OERSTED'S TWISTED COMPASS NEEDLE." "AN ELECTRIC SWITCH CLOSED IN ONE PLACE" "COULD CAUSE A MAGNET TO MOVE IN ANOTHER PLACE." "OTHERS SOON CAME TO THE SAME REALIZATION." "THE TELEGRAPH HELD THE PROMISE" "OF ALMOST INSTANTANEOUS LONG-DISTANCE COMMUNICATION." "BUT IN THE BEGINNING," "THE PROMISE OF LONG-DISTANCE CALLING" "WAS SHORT-LIVED." "AFTER TRAVELING A FEW KILOMETERS," "THE SIGNAL WAS TOO WEAK TO ACTIVATE THE MAGNETIC DEVICE." "THAT PROBLEM WAS SOLVED BY CHARLES WHEATSTONE," "A MUSICAL INSTRUMENTMAKER AND A STUDENT OF ACOUSTICS." "HE FOUND THE SOLUTION TO THIS DILEMMA" "IN THE ALMOST UNINTELLIGIBLE WRITINGS" "OF AN OBSCURE GERMAN PROFESSOR" "NAMED GEORG SIMON OHM." "WHAT OHM HAD PREDICTED" "WITH ABSTRACT MATHEMATICAL REASONING," "WHEATSTONE SHOWED THROUGH DIRECT EXPERIMENT." "THE SIGNAL CAN BE KEPT THE SAME SIZE" "IF THE VOLTAGE IS INCREASED IN PROPORTION TO THE DISTANCE." "WHEATSTONE HAD VERIFIED THE RULE KNOWN AS OHM'S LAW." "TOMAKEACURRENTFLOW  THROUGHA CONDUCTINGMATERIAL," "AVOLTAGEIS NEEDED." "THECURRENTIS ALWAYS PROPORTIONAL TO THE VOLTAGE." "THE CONSTANT OF PROPORTIONALITY" "ISCALLEDTHERESISTANCE." "THISEQUATION" "ISKNOWNOHM'SLAW ." "ANELEMENTIN AN ELECTRIC" "CIRCUITWITHRESISTANCE" "ISCALLEDARESISTOR." "OHM'S LAW ISN'T A FUNDAMENTAL LAW OF NATURE" "LIKE NEWTON'S SECOND LAW" "OR THE LAW OF CONSERVATION OF ENERGY." "IT DOESN'T HOLD IN ALL SITUATIONS," "BUT IT'S A USEFUL RULE IN MOST PRACTICAL SITUATIONS." "IT HELPED TURN THE TELEGRAPH" "INTO A VERY PRACTICAL INVENTION INDEED." "WITH EDISON'S REFINEMENTS" "AND THE CODE DEVISED BY SAMUEL MORSE," "THE TELEGRAPH PUSHED BACK THE AMERICAN FRONTIER" "AND TOOK THE TRAIN WITH IT." "TELEGRAPH WIRES PARALLELED THE TRACKS," "AND THE INFORMATION THEY CARRIED WAS ESSENTIAL" "TO THE SMOOTH RUNNING OF THE ENTIRE RAILROAD SYSTEM." "NOT THAT THERE WASN'T RESISTANCE" "TO THE USE OF BOTH OF THESE INVENTIONS." "PEOPLE SAID ELECTRICITY WAS DANGEROUS," "AND SOME SAID THAT" "AT THE FAST SPEEDS TRAINS COULD TRAVEL," "HUMANS WOULDN'T BE ABLE TO BREATHE." "BUT THERE WAS NO STOPPING PROGRESS." "AND IN THE LONG RUN, WIRES AND RAILS TOGETHER" "PLAYED THE SAME VITAL ROLE RIVERS HAD LONG PLAYED" "TRANSPORTERS OF PEOPLE, CARGO, AND IDEAS." "AND THROUGH MILES AND MILES OF WIRE," "THE FLOW OF INFORMATION FOLLOWS" "FROM THE PRACTICAL USE OF OHM'S LAW." "IN MUCH THE SAME WAY," "SIMILAR RULES LEAD HYDRAULIC ENGINEERS" "IN THE DESIGN AND OPERATION OF AQUEDUCTS." "THOSE ENGINEERS HAVE LONG KNOWN THAT THE RATE" "AT WHICH WATER FLOWS THROUGH A PIPE" "DEPENDS ON JUST A HANDFUL OF FACTORS" "THE SLOPE OF THE LAND AND THE PRESSURE APPLIED," "THE LENGTH AND DIAMETER OF THE PIPE," "AND THE VISCOSITY AND DENSITY OF WATER." "IN PRECISE ANALOGY," "THE AMOUNT OF ELECTRIC CURRENT" "THAT FLOWS THROUGH A RESISTOR" "DEPENDS ON THE VOLTAGE DROP" "ACROSS IT" "HOW WIDE AND HOW LONG IT IS," "AND WHAT IT'S MADE OF." "THERESISTANCEOF  ANELECTRICRESISTOR" "ISPROPORTIONAL TOITSLENGTH..." "INVERSELYPROPORTIONAL TOITSAREA..." "ANDPROPORTIONAL TOITSRESISTIVITY," "OR ITS TENDENCY TO INHIBIT THEFLOWOF ELECTRONS." "THISTENDENCYTO RESIST" "ISSOMETHING ALLMATERIALSHAVE," "BUTTOVARYINGDEGREES." "ADDINGRESISTORSTO ACIRCUIT, ONEAFTERANOTHER," "HASTHESAMEEFFECT ASMAKINGONERESISTORLONGER." "THESEARECALLED RESISTORSINSERIES." "PUTTINGRESISTORSSIDE-BY-SIDE INCREASESTHEAREA" "THROUGHWHICH THECURRENTCANFLOW." "THESEARECALLED RESISTORSINPARALLEL." "THEY HAVE A LOWER RESISTANCE THANEITHERONEALONE." "THE SAME IS TRUE OF WATER." "ADDING SECTIONS OF PIPE IN A SERIES" "IS THE SAME AS MAKING IT LONGER," "AND SO THE RESISTANCE TO MOVEMENT INCREASES." "BUT IF THE PIPES ARE ADDED SIDE-BY-SIDE," "THEY CAN CARRY MORE WATER MORE EASILY." "AND THESE PARTICULAR PIPES CARRY A LOT OF WATER," "LIFTING IT UP 1,600 FEET FROM THE COLORADO RIVER" "TO A POINT WHERE IT CAN FLOW DOWN TO LOS ANGELES." "HOWEVER, BECAUSE THE DAM AND PUMPING STATION" "WERE DESIGNED TO CARRY AWAY SO MUCH WATER," "THE PROJECT ITSELF ENCOUNTERED SOME STIFF RESISTANCE," "ESPECIALLY FROM ARIZONA," "THE STATE WHICH HAPPENS TO BE ON THE OTHER SIDE OF THE RIVER." "ON THE DAY CONSTRUCTION BEGAN IN 1934," "THE ARIZONA STATE MILITIA PERCHED ON THE RIM OF THE RIVER" "WITH RIFLES AND MACHINE GUNS." "IN THIS CASE," "THE BASIS FOR RESISTANCE WAS CLEAR" "THE FLOW OF PROGRESS FOR CALIFORNIA" "WAS AT THE EXPENSE OF ARIZONA'S FUTURE." "BUT WHAT ABOUT THE NATURAL RESISTANCE" "TO THE PROGRESS OF ELECTRONS?" "JUST WHAT IS THE NATURE OF ELECTRICAL RESISTANCE?" "UNDER THE INFLUENCE OF AN ELECTRIC FIELD," "ELECTRONS MOVE THROUGH A METAL" "MUCH AS A MARBLE FALLS THROUGH A VISCOUS FLUID." "IF IT WEREN'T FOR RESISTANCE, THEY WOULD ACCELERATE FREELY," "LIKE A FALLING BODY IN A VACUUM." "BUT, AS IT IS, THEY MOVE, ON THE AVERAGE," "AT A CONSTANT SPEED." "RESISTIVITY IS LIKE VISCOSITY" "THE MORE OF IT A MATERIAL HAS," "THE SLOWER A PARTICLE WILL MOVE THROUGH IT." "BUT WHAT SLOWS THE ELECTRONS DOWN?" "IN OTHER WORDS, IN A CONDUCTOR," "WHAT RESISTS THE FLOW OF ELECTRICITY?" "INSIDE A METAL," "ELECTRONS CONSTANTLY MOVE IN ALL DIRECTIONS." "HERE, JUST A FEW OF THEM ARE REPRESENTED AS DOTS." "THEY ORBIT THROUGH THE METAL" "AS IF IT WERE ONE GIANT MOLECULE." "THIS KIND OF FLOW ENCOUNTERS NO RESISTANCE," "NOR DOES IT CREATE" "A NET FLOW IN ONE END AND OUT THE OTHER." "UNDER THESE CONDITIONS," "THE CONDUCTOR IS IN ELECTROSTATIC EQUILIBRIUM." "THERE'S NO ELECTRIC FIELD INSIDE," "NO VOLTAGE DIFFERENCE FROM ONE END TO THE OTHER." "BUT IF A BATTERY MAKES AN ELECTRIC CURRENT FLOW," "EQUILIBRIUM IS DESTROYED," "AND AN ELECTRIC FIELD IS CREATED INSIDE THE CONDUCTOR." "INSIDE A PERFECT CRYSTALLINE METAL," "IF A SAMPLE OF IT COULD BE FOUND," "THE MOBILE ELECTRONS WOULD CONTINUOUSLY ACCELERATE" "LIKE A PENNY FALLING IN A VACUUM." "BUT IN THE REAL WORLD, CRYSTALS AREN'T PERFECT." "THEY HAVE DEFECTS AND IMPURITIES," "AND THEIR ATOMS VIBRATE WITH THERMAL ENERGY." "ELECTRONS, ACCELERATED BY THE FORCE OF THE ELECTRIC FIELD," "BOUNCE OFF EACH IMPERFECTION," "BEHAVING SOMEWHAT LIKE A BALL IN A PINBALL MACHINE." "ALL THAT BOUNCING," "ALL THAT STOPPING AND RESTARTING," "PRODUCES THE RESISTANCE" "THAT PREVENTS THE ELECTRON FLOW FROM BUILDING UP SPEED." "SO THE ELECTRONS MOVE AT A CONSTANT AVERAGE SPEED," "CREATING A CONSTANT CURRENT," "UNDER THE INFLUENCE OF A CONSTANT FORCE." "AS THE ELECTRONS BOUNCE OFF THE IMPERFECTIONS," "THEY SET THE ATOMS INTO LARGER VIBRATIONS." "SO THE ELECTRICAL ENERGY OF ACCELERATED ELECTRONS" "TURNS INTO THE HEAT ENERGY OF VIBRATING ATOMS." "AND ABOUT 100 YEARS AGO," "A BRILLIANT IDEA ROSE FROM THAT HEAT." "IF A RESISTOR GETS HOT ENOUGH, IT WILL GLOW," "AND THOMAS EDISON FOUND JUST THE RIGHT MATERIALS" "THAT WOULD GLOW BRIGHTLY." "OF COURSE, ALL CIRCTS DON'T GLOW," "BUT THEY ALL PRODUCE HEAT, WHETHER IT'S WANTED OR NOT." "IN COMPUTERS, FOR INSTANCE," "FANS ARE USED TO ELIMINATE UNWANTED HEAT." "IN FACT, SOME SUPERCOMPUTERS GENERATE SO MUCH HEAT" "THAT THEY REQUIRE A LIQUID COOLING SYSTEM" "TO KEEP THE TEMPERATURE DOWN." "WHETHER HEAT IS THE GOAL OR AN UNWANTED BY-PRODUCT," "IT TAKES POWER TO PRODUCE IT." "ASCURRENTFLOWS" "THROUGHA RESISTOR," "THE ENERGY TURNED INTO HEAT" "ISEQUALTO THEAMOUNT" "OFCHARGETHATFLOWS" "TIMESTHECHANGEINPOTENTIAL." "THERATEOF HEATING," "ORPOWERCONSUMED," "ISEQUALTO" "THECURRENTTIMESTHE VOLTAGE." "USINGOHM'SLAW," "THE POWER CAN ALSO BE WRITTEN" "ASI SQUAREDR," "ORV SQUARED/R." "AND WHAT'S THE RESULT?" "WELL, TO START WITH, IT'S MEASURED IN WATTS." "1 WATT IS A MEASURE OF POWER EQUAL TO 1 AMP TIMES 1 VOLT." "MULTIPLY THAT WATT BY 1,000 TO GET KILOWATTS." "MULTIPLY THAT BY 1,000 AGAIN" "TO GET MEGAWATTS." "AT PEAK HOURS," "PARKER DAM GENERATES 120 MEGAWATTS." "WATTS AND WATER." "THE ELECTRIC GRID AND THE WATER SYSTEM" "IT'S A POWERFUL ANALOGY THAT TAKES CONCRETE SHAPE" "HERE IN THIS HYDROELECTRIC GENERATING PLANT." "IF PROGRESS RIDES THE CURRENTS" "OF WATER AND ELECTRICITY," "IT ALSO DEMANDS A LOT OF EACH." "IN AMERICA'S ENERGY-HUNGRY SOCIETY," "EACH PERSON CONSUMES ABOUT A KILOWATT OF ELECTRIC POWER" "ALL THE TIME, DAY IN AND DAY OUT, ALL YEAR LONG." "AND EACH FAMILY CONSUMES ABOUT AN ACRE-FOOT OF WATER" "THAT IS, ALL THE WATER IN ONE ACRE OF LAND" "COVERED TO A DEPTH OF ONE FOOT, EVERY YEAR." "TO DELIVER BOTH WATER AND POWER TO THE CONSUMERS," "ENGINEERS MUST FIRST MASTER" "THE ART AND SCIENCE OF CIRCUIT DESIGN." "THE COMMON ELEMENTS OF ELEMENTARY ELECTRIC CIRCUITS" "ARE WIRES AND SWITCHES," "BATTERIES, RESISTORS, AND CAPACITORS." "AND WHILE THESE ELEMENTS CAN BE COMBINED" "INTO NETWORKS OF EVER INCREASING COMPLEXITY," "THEY ALWAYS OBEY THE SAME SIMPLE RULES" "CALLED KIRCHHOFF'S LAWS." "GUSTAV KIRCHHOFF, A GERMAN PHYSICIST," "WAS KEEN ON MATHEMATICS." "BY APPLYING OHM'S LAW" "AND GENERALIZING IT FULLY," "HE DERIVED TWO LAWS," "AND EACH EXPRESSES A FAMILIAR IDEA." "ONE OF THOSE IDEAS IS CONSERVATION OF CHARGE." "AND THE CORRESPONDING LAW FOR CIRCUITS IS" "WHENEVER ONE CURRENT SPLITS INTO TWO, OR VICE VERSA," "THE TOTAL CURRENT INTO THE JUNCTION" "WILL EQUAL THE TOTAL CURRENT OUT OF IT." "KIRCHHOFF'S OTHER LAW" "EXPRESSES CONSERVATION OF ENERGY." "AN ELECTRIC CHARGE GOING AROUND ANY COMPLETE CIRCUIT" "NEITHER GAINS NOR LOSES ENERGY." "CONSIDER AN ELECTRIC CHARGE IN SPACE" "NOT CONFINED TO A CIRCUIT." "IF IT'S MOVED THROUGH SPACE ON A PATH" "THAT BRINGS IT BACK TO ITS STARTING POINT," "NO NET WORK IS DONE." "THE ELECTRIC POTENTIAL, OR VOLTAGE," "MAY GO UP OR DOWN," "BUT IT ALWAYS GETS BACK TO WHERE IT STARTED." "THE SAME IS TRUE INSIDE A CIRCUIT." "NOTICE THAT AN INTEGRAL ALONG A CLOSED PATH" "HAS A SPECIAL NOTATION" "AN INTEGRAL SIGN WITH A CIRCLE ON IT." "SO, IN THE SPECIAL CASE OF AN ELECTRIC CIRCUIT," "ALL THE VOLTAGE RISES" "DUE TO BATTERIES AND CHARGED CAPACITORS" "AND ALL THE VOLTAGE DROPS" "DUE TO CURRENTS FLOWING THROUGH RESISTORS" "ADD UP TO ZERO." "USING THESE TWO LAWS ALONE," "ENGINEERS ANALYZE THE MOST COMPLEX CIRCUITS." "TO TAKE JUST A SIMPLE EXAMPLE," "CONSIDER A CAPACITOR" "CONNECTED TO A RESISTOR AND A BATTERY." "EVEN AS THE CAPACITOR CHARGES," "THE TOTAL RISE IN VOLTAGE" "EQUALS THE TOTAL FALL AROUND THE CIRCUIT." "A CAPACITOR IN AN ELECTRIC CIRCUIT STORES CHARGE," "MUCH THE SAME WAY" "A RESERVOIR STORES WATER FOR LATER USE." "IT TAKES TIME TO FILL OR EMPTY EITHER ONE." "HOW MUCH TIME?" "THAT DEPENDS, OF COURSE, ON HOW BIG THE RESERVOIR IS" "AND HOW MUCH RESISTANCE" "THERE IS TO THE WATER FLOWING OUT." "THE BIGGER THE RESERVOIR AND THE MORE THE RESISTANCE," "THE LONGER IT WILL TAKE." "THE SAME IS TRUE OF CHARGE DRAINING FROM A CAPACITOR." "APPLYING KIRCHHOFF'S LAWS, THE TIME IS FOUND TO BE EQUAL" "TO THE CAPACITANCE TIMES THE RESISTANCE." "OF COURSE, THERE ARE NO IMMEDIATE PLANS" "TO DRAIN LAKE HAVASU." "AS FAST AS WATER IS DRAINED" "TO QUENCH THE THIRST OF LOS ANGELES," "SNOW FROM DISTANT MOUNTAINS MELTS TO FEED THE COLORADO," "WHICH IN TURN REFILLS THE RESERVOIR" "AS PART OF A GLOBAL CYCLE THAT CONSERVES MOISTURE" "MUCH AS ELECTRIC CIRCUITS CONSERVE CHARGE." "AND SO TO THE NOTION OF PROGRESS" "IS ADDED THE PRINCIPLE OF CONSERVATION," "PERHAPS PROVING THAT THE MORE THINGS CHANGE," "THE MORE THEY STAY THE SAME." "CIVILIZATION STILL DEPENDS ON CURRENTS," "THOUGH THE FLOW OF ELECTRICITY HAS BEEN ADDED." "AND THE MODERN CITY, AS MUCH AS ANCIENT ROME," "DEPENDS UPON AND IS LIMITED BY" "THE ABILITY TO CHANNEL AND DISTRIBUTE THOSE CURRENTS." "TODAY WE'VE STUDIED THE RULES THAT MAKE ELECTRICITY PRACTICAL." "THEY WERE FIRST WORKED OUT" "BY PEOPLE NAMED OHM AND KIRCHHOFF" "AND CHARLES WHEATSTONE." "WHEATSTONE HIMSELF WAS REVERED BY HIS COLLEAGUES" "IN HIS OWN TIME," "BUT HE WAS UNKNOWN TO THE PUBLIC." "HE WAS A SHY MAN" "AND MORBIDLY TIMID IN FRONT OF AN AUDIENCE" "JUST LIKE ME." "IN FACT, THAT WAS THE CAUSE, THE WAY," "IN WHICH HE MANAGED TO CHANGE" "THE TRADITION OF PUBLIC LECTURES AT THE ROYAL INSTITUTION." "APPARENTLY, ONE EVENING IN 1846," "IT WAS CHARLES WHEATSTONE" "WHO WAS TO GIVE THAT EVENING'S PUBLIC LECTURE." "BUT AT THE VERY LAST SECOND," "WITH THE AUDIENCE ALREADY IN THEIR SEATS," "WHEATSTONE PANICKED AND FLED," "LEAVING NOBODY TO GIVE THE LECTURE." "WELL, MICHAEL FARADAY STEPPED IN" "AND GAVE A BRILLIANT IMPROMPTU LECTURE," "SPECULATING THAT LIGHT MIGHT BE" "SOME KIND OF A DISTURBANCE OF ELECTRICITY AND MAGNETISM," "AN IDEA PROVED RIGHT MANY YEARS LATER." "THAT TRADITION OF PUBLIC LECTURES" "AT THE ROYAL INSTITUTION CONTINUES TO THIS VERY DAY." "EVERY FRIDAY EVENING AT 8:00 ON THE DOT," "A CELEBRATED SCIENTIST," "DRESSED JUST LIKE THIS, IN FORMAL ATTIRE," "STEPS OUT BEFORE A GLITTERING AUDIENCE" "TO DELIVER A LECTURE" "ON THE LATEST DEVELOPMENTS IN SCIENCE." "BUT FOR A HALF HOUR BEFORE THE LECTURE," "THAT SCIENTIST HAS BEEN KEPT LOCKED IN A LITTLE ROOM" "TO MAKE SURE HE DOESN'T "DO A WHEATSTONE"" "AT THE VERY LAST MINUTE." "THAT'S WHY I WAS KEPT LOCKED IN THAT ROOM" "UNTIL THE BEGINNING OF THIS LECTURE." 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