Simbool op nutspaal op foto uit 1906

Simbool op nutspaal op foto uit 1906

Ek het toevallig hierdie simbool opgemerk:

op 'n gebruikspaal op 'n foto uit 1906.

Wat beteken die simbool?


Is dit 'n vereenvoudigde logo van die logo van die Portland Railway Light and Power Company? Volgens hierdie webwerf het hulle die elektriese dienste in 1906 aan sommige kliënte in Salem oorgeneem (sien hieronder)

1906: Portland kry sy eerste bioskoop. PGE smelt saam met Portland Railway Company en die Oregon Water Power & Railway Company om Portland Railway Light & Power Co (PRL & P) te word - die eienaar en operateur van stads- en voorstedelike elektriese spoorwegdienste; PRL & P koop kragondernemings en neem elektriese diens oor aan Washington -kliënte in Vancouver en Oregon -kliënte in Salem, Mount Angel, Silverton en Woodburn. Cazadero/Faraday plant


Dit lyk soos 'n watermerk of iets soortgelyks, óf bo -op die foto self aangebring, óf op 'n stadium bygevoeg tydens die omskakeling van die foto in digitale formaat. Dit behou nie dieselfde skaduwee as op die boom self nie (veral daar is 'n klein skaduwee wat daaroor sou loop as dit eintlik 'n deel van die oorspronklike foto was). Alhoewel dit min of meer op die boom gesentreer is, is dit nie so nie presies gesentreer en 'n mens sou verwag dat die vorm van die driehoek so effens verdraai sou word deur die kromming van die boom as dit inderdaad daarop sit (dit lyk eintlik asof dit 'dryf'), daarom het ek dink dit is 'n ekstra-fotografiese artefak). Dit is ook langs die linkerkantlyn, nie 'n buitengewone plek om so 'n merk te plaas nie, en dit lyk vir my 'n helderder wit skakering as enigiets anders op die foto.


Hidro -elektriese krag: hoe dit werk

So, hoe kry ons elektrisiteit uit water? Eintlik produseer hidro-elektriese en steenkoolkragsentrales elektrisiteit op 'n soortgelyke manier. In beide gevalle word 'n kragbron gebruik om 'n propelleragtige stuk, 'n turbine, te draai.

Vallende water produseer hidro -elektriese krag.

Krediet: Tennessee Valley Authority

So, hoe kry ons elektrisiteit uit water? Eintlik produseer hidro-elektriese en steenkoolkragsentrales elektrisiteit op 'n soortgelyke manier. In beide gevalle word 'n kragbron gebruik om 'n propelleragtige stuk turbine te draai, wat dan 'n metaalas in 'n elektriese kragopwekker draai, wat die motor is wat elektrisiteit produseer. 'N Steenkoolkragstasie gebruik stoom om die turbine se lemme te draai terwyl a hidro -elektriese aanleg gebruik vallende water om die turbine te draai. Die resultate is dieselfde.

Kyk na die diagram (met vergunning van die Tennessee Valley Authority) van 'n hidro -elektriese kragstasie om die besonderhede te sien:

Die teorie is om 'n dam op 'n groot te bou rivier met 'n groot daling in hoogte (daar is nie baie hidro -elektriese aanlegte in Kansas of Florida nie). Die dam stoor baie water daaragter in die reservoir. Naby die bodem van die damwal is die waterinname. Swaartekrag veroorsaak dat dit deur die pen in die dam val. Aan die einde van die penhouer is daar 'n turbine -dryfveer wat deur die bewegende water gedraai word. Die as van die turbine gaan in die kragopwekker wat die krag produseer. Kraglyne is gekoppel aan die kragopwekker wat elektrisiteit na u huis en myne vervoer. Die water loop verby die dryfveer deur die stertlyn tot by die rivier verby die dam. Terloops, dit is nie 'n goeie idee om in die water reg onder 'n dam te speel as water vrykom nie!

'N Turbine en kragopwekker produseer die elektrisiteit

Diagram van 'n hidro -elektriese turbine en kragopwekker.

Krediet: Amerikaanse weermagkorps van ingenieurs

Oor hoe hierdie kragopwekker werk, verduidelik die Corps of Engineers dit so:
"'N Hidrouliese turbine skakel die energie van vloeiende water om in meganiese energie.' N Hidro -elektriese kragopwekker skakel hierdie meganiese energie om in elektrisiteit. Die werking van 'n kragopwekker is gebaseer op die beginsels wat Faraday ontdek het. Hy het gevind dat wanneer 'n magneet by 'n geleier verby beweeg word, Dit veroorsaak dat elektrisiteit vloei. In 'n groot kragopwekker word elektromagnete gemaak deur gelykstroom te sirkuleer deur draadlusse wat om stapels magnetiese staallaminasies gewikkel is. Dit word veldpale genoem en is op die omtrek van die rotor gemonteer. Die rotor is vasgemaak na die turbine -as, en draai teen 'n vaste spoed. As die rotor draai, veroorsaak dit dat die veldpale (die elektromagnete) verby die geleiers in die stator beweeg. Dit veroorsaak weer elektrisiteit en 'n spanning ontwikkel by die generator se uitgangsterminale. "

Gepomp berging: hergebruik van water vir die hoogste vraag na elektrisiteit

Die vraag na elektrisiteit is nie 'plat' en konstant nie. Die vraag styg gedurende die dag, en oornag is daar minder elektrisiteit in huise, besighede en ander geriewe nodig. Byvoorbeeld, hier in Atlanta, Georgia, om 17:00 op 'n warm naweekdag in Augustus, kan u wed dat daar 'n groot vraag na elektrisiteit is om miljoene lugversorgers te bestuur! Maar 12 uur later om 05:00. nie soseer nie. Hidro-elektriese aanlegte is meer doeltreffend om in kort tydperke te voorsien in piekkragbehoeftes as fossielbrandstof- en kernkragaanlegte, en een manier om dit te doen is deur gebruik te maak van "gepompte berging", wat dieselfde water meer as een keer hergebruik.

Gepompte berging is 'n metode om water in die reservaat te hou vir kragvereistes in die spitstyd deur water wat reeds deur die turbines gevloei het, terug te voer na 'n opbergpoel bo die kragsentrale op 'n tydstip waarop die verbruikers se vraag na energie laag is, soos in die middel Van die nag. Die water word dan toegelaat om terug te vloei deur die turbine-kragopwekkers op tye wanneer die vraag groot is en 'n groot las op die stelsel geplaas word.

Gepomp berging: hergebruik van water vir die hoogste vraag na elektrisiteit

Die reservoir werk baie soos 'n battery, wat krag in die vorm van water stoor as die behoeftes laag is en maksimum krag lewer tydens daaglikse en seisoenale spitstye. 'N voordeel Die gepompte berging is dat hidro -elektriese opwekkingseenhede vinnig kan begin en die produksie vinnig kan aanpas. Hulle werk doeltreffend as dit vir een uur of 'n paar uur gebruik word. Omdat gepompte opbergingsreservoirs relatief klein is, is die boukoste oor die algemeen laag in vergelyking met konvensionele waterkraggeriewe.


Historiese noot Keer terug na Bo

A. Russell Mortensen het sy tyd tussen Utah en Kalifornië verdeel en sy vroeë professionele jare as onderwyser, administrateur en redakteur deurgebring. Hy is gebore in Salt Lake City vir Arlington Peter en Fannie Burnham Mortensen op 30 Januarie 1911 en is grootgemaak in die suide van Kalifornië. Mortensen het in die vroeë 1930's na Utah teruggekeer om die Brigham Young University by te woon. Terwyl hy daar was, ontmoet en trou hy met Bessie Burch, 'n boorling van Spanish Fork, Utah. Nadat hy in 1937 'n BS in die geskiedenis ontvang het, word Mortensen vir 'n jaar skoolhoof van die Garfield County Cannonville School.

Die Mortensens het twee jaar in Kalifornië deurgebring terwyl hy aan 'n meestersgraad gewerk het, in 1940 toegeken aan die Universiteit van Kalifornië in Los Angeles, voordat hy na Utah teruggekeer het. Die volgende ses jaar was Mortensen 'n geskiedenisinstrukteur aan die Hoërskool Provo. Sy onderrig is tydens die Tweede Wêreldoorlog onderbreek toe hy in die Stille Oseaan -teater as vlootkommunikasiebeampte gedien het.

Na die oorlog keer die egpaar weer terug na Kalifornië en Mortensen keer terug na die U.C.L.A. kampus. Die volgende vier jaar werk Mortensen aan 'n doktorsgraad in geskiedenis as onderwysassistent by U.C.L.A. en later as instrukteur van die Amerikaanse en Latyns -Amerikaanse geskiedenis aan die San Bernardino Valley College. Terwyl hy in San Bernardino was, het Mortensen sy verbintenis met die Amerikaanse vloot voortgesit as die assistent -opleidingsbeampte by die U.S. Naval Reserve Training Center.

A. Russell Mortensen het sy Ph.D. aan die Universiteit van Kalifornië in Los Angeles in 1950. Dieselfde jaar sterf sy vrou, Bessie, na die geboorte van hul sesde kind. Met hierdie slag het Mortensen sy gesin na Utah verwyder, waar hy die pos aanvaar het as direkteur van die Utah Historical Society en redakteur van sy tydskrif Utah Historical Quarterly. Gedurende sy elf jaar as direkteur skryf hy 'n aantal artikels vir die Utah Historical Quarterly, ander tydskrifte en plaaslike koerante. In 1958 die boek Onder die Mormone, wat saam met William Mulder geskryf is, is gepubliseer. Dit is ook gedurende hierdie jare dat hy met Florence Page getroud is.

In 1961 word Mortensen direkteur van die University of Utah Press en professor in geskiedenis en biblioteekwetenskap aan die universiteit. Die Western History Association en die universiteit het 'n nuwe kwartaallikse tydskrif, die Amerikaanse Weste, waarvoor Mortensen gedien het as redakteur tussen 1962 en 1967. Terwyl hy redakteur was, sterf sy tweede vrou en trou hy met Dorothy Zackrison Summerhays.

Na sy bedanking as redakteur van die Amerikaanse Weste as gevolg van 'n polemiek oor sy moontlike belangebotsing as aandeelhouer in die nuwe American West Publishing Company, het Mortensen voortgegaan om klas te gee aan die Universiteit van Utah. Hy was ook 'n besoekende professor aan die Universiteit van Alabama. Gedurende sy jare by die universiteit was hy betrokke by ander historiese projekte. In 1969 dien hy as 'n lid van die raad van die Utah Historic Survey Committee. Met sketse deur Carlos Andreson het die University of Utah Press Mortensen's gepubliseer Vroeë Utah -sketse in 1970.

Tussen 1970 en 1976 werk Mortensen in Washington, DC saam met die National Park Service as assistent en daarna hoofhistorikus. Hy was ook die direkteur van die NPS Historic Site Preservation Program en 'n adviesraadslid vir die "State and the National Bicentennial Series."

Die Amerikaanse Vereniging vir Staats- en Plaaslike Geskiedenis, waarvoor hy as raadslid, hoofredakteur, sekretaris en president gedien het, het hom in 1979 'n toekennings toekenning vir sy werk op historiese gebied toegeken. Hierdie een het by sy toekennings aangesluit vir die Amerikaanse Weste, die Joint Award of Merit met die Utah Historical Society, en sy toekenning as mede-outeur van Onder die Mormone.

Gedurende sy loopbaan dien Mortensen by 'n aantal Utah -groepe, waaronder die Family Service Society, die State Parks Commission, die State Library Commission en die Utah Folklore Society. Hy was ook lid van professionele en spesiale belangorganisasies wat die Western History Association, die American Association for State and Local History, Utah Westerners 'Club en die Utah Sons of Pioneers insluit.

Inhoudbeskrywing Keer terug na Bo

Die A. Russell Mortensen-vraestelle (1830-1996) bestaan ​​uit die persoonlike en professionele referate van Mortensen (geb. 1911), 'n onderwyser, administrateur en redakteur. Die klein hoeveelheid persoonlike materiaal bestaan ​​uit 'n paar briewe van familie -kole, briewe oor sy diens in die vlootreservaat en inligting oor die beskikking van die boedel van Mary Burnham Jones. Die eerste boks bevat hierdie persoonlike materiaal sowel as alfabeties gerangskikte korrespondensie van vriende en kennisse. Hierdie briewe bevat nie materiaal wat verband hou met ander dele van die versameling nie.

Mortensen het gedurende sy loopbaan 'n aantal professionele posisies beklee. Korrespondensie en inligting oor hierdie poste, alfabeties gerangskik volgens organisatoriese titel, word saamgevoeg in raam 2. Ook in hierdie gedeelte is aansoeke en korrespondensie oor 'n aantal poste waarvoor Mortensen aansoek gedoen het. Daar is 'n klein kronologiese aanbevelingslêer wat Mortensen tussen 1968 en 1970 geskryf het.

Daar is vier bokse alfabeties gerangskikte materiaal van organisasies waarvan Mortensen lid was. Hierdie lêers bevat korrespondensie, lidmaatskapinligting, algemene inligting oor die organisasie, komiteeverslag en aanbevelings en ander diverse materiaal.

Een boks met manuskripte, artikels en publikasie -inligting bevat 'n konsep van Vroeë Utah -sketse, geskryf deur Mortensen en geïllustreer met sketse deur Carlos Andreson (University of Utah Press, 1970). Daar is afskrifte van 'n aantal kort artikels wat deur Mortensen in Utah -koerante gepubliseer is terwyl hy die direkteur van die Utah State Historical Society was. Ook korrespondensie oor die boek van C. Gregory Crampton Staande land, en afskrifte van manuskripte oor Utah en die Kerk van Jesus Christus van die Heiliges van die Laaste Dae, geskryf deur ander mense as Mortensen.

Onder die Mormone, wat in 1958 gepubliseer is, is in samewerking met William Mulder geskryf. Daar is drie verskillende konsepte van die boek ingesluit: 'n finale konsep, 'n volledige manuskrip met knip-en-plak-hersienings en 'n onvolledige konsep met skriftelike hersienings van die voorblaaie en die eerste drie afdelings van hierdie bloemlesing. Daar is drie bokse materiaal waaruit die gedeeltes uit die boek geneem is. Aangesien al hierdie voorheen gepubliseerde materiaal alfabeties volgens skrywer gerangskik is, verskyn dit nie weer in die indeks nie.

Die grootste deel van die versameling bestaan ​​uit die lêers oor die Amerikaanse Weste tydskrif. Ses bokse materiaal dek die sake van die publikasie. Ingesluit is korrespondensie en ander inligtingsmateriaal wat handel oor finansies, regsprobleme, produksie en promosie van tydskrifte en allerhande verwante onderwerpe.

Onder die borgskap van die Western History Association en die Universiteit van Utah is die publikasie en promosie van die tydskrif deur Lane Book Company onderneem. In 1965 word 'n nuwe maatskappy, American West Publishing Company, gestig om die funksie oor te neem. Die sakelêers bevat korrespondensie oor die omstredenheid wat ontstaan ​​het omdat personeellede wat betaalde posisies by die Universiteit beklee en werk aan die Amerikaanse Weste het baat by die behoud van voorraad in die nuwe uitgewery. Op hierdie stadium bedank Mortensen as redakteur, en die lêers bevat baie min na-datering 1967.

Die volgende twintig bokse bevat manuskripte en korrespondensie wat gestuur is aan A. Russell Mortensen as redakteur van die Amerikaanse Weste. In sewentien hiervan is manuskripte wat in die tydskrif gepubliseer is, en korrespondensie. Die briewe bevat die oor die manuskripte, baie wat vra oor moontlike publikasie, die van die tydskrif tot uitgewerye wat soek na boeke wat hersien moet word en 'n paar wat ander soorte inligting soek of herdrukke van artikels wat in die tydskrif verskyn. Die ander drie bokse bevat manuskripte en gepaardgaande korrespondensie, wat om verskillende redes ingedien is, is nooit gepubliseer nie. Hierdie ongepubliseerde manuskripte is beskikbaar vir navorsingsgebruik, maar mag nie sonder skriftelike toestemming van die outeur gekopieer word nie. Al die manuskripte en korrespondensie is alfabeties gerangskik. As gevolg van hierdie reëling verskyn nie alle name weer in die indeks nie.

Sommige van die manuskripte, beide gepubliseer en ongepubliseer, het gepaard gegaan met redaksionele kommentaar of evaluering van personeel. Op grond van 'n brief van die assistent -prokureur -generaal aan die Universiteit van Utah, is hierdie evaluerings en kommentaar as vertroulik verklaar en tot geslote lêers verwyder tot 2017.

Die laaste gedeelte van die versameling bevat referate wat tydens die Noord -Amerikaanse bonthandelkonferensie in 1965 gegee is. Sommige van hierdie artikels is gepubliseer in 'n bundel met die titel Aspekte van die bonthandel: geselekteerde referate van die Noord -Amerikaanse bonthandelkonferensie in 1965 (Minnesota Historical Society, St. Paul, 1967). Hierdie word alfabeties saamgevoeg. Die oorblywende, ongepubliseerde vraestelle word ook in alfabetiese volgorde ingedien en mag vir navorsingsdoeleindes gebruik word, maar nie sonder skriftelike toestemming van die outeur gekopieer word nie.

Byvoegings tot die versameling bevat korrespondensie, subsidievoorstelle, geskrifte, nuusuitknipsels en materiaal oor die Westerse geskiedenis.

Gebruik van die versameling Keer terug na Bo

Beperkings op gebruik

GEEN FOTOKOPIËR TOEGELAAT UIT BOX 41.

Die biblioteek beweer nie dat dit die outeursreg op alle materiaal in die versameling beheer nie. 'N Persoon wat in 'n reproduksie uitgebeeld word, het privaatheidsregte soos uiteengesit in titel 45 CFR, deel 46 (Protection of Human Subjects). Raadpleeg die gebruiksooreenkoms van J. J. Willard Marriott -biblioteek en vorms vir reproduksieversoek vir meer inligting.

Aanbevole aanhaling

Versamelingsnaam, versamelingsnommer, boksnommer, gidsnommer. Spesiale versamelings, J. Willard Marriott Library, The University of Utah.

Administratiewe inligting Keer terug na Bo

Verkrygingsinligting

Boxes 1-43 is in 1972 geskenk (18 lineêre voet).

Boxes 44-47 is in 1982 geskenk (2 lineêre voet).

Boxes 48-57 is in 1993 en 1996 geskenk (5 lineêre voet).

Verwerkingsnota

Verwerk deur Marlene Lewis en Kate Kimball in 1980-2002.

Afgesonderde materiale

Foto's en oudio-visuele materiaal is oorgedra na die Multimedia-afdeling vir spesiale versamelings (P0201 en A0417).


Simbool op nutspaal op foto uit 1906 - Geskiedenis

Die geval van die elektron bring verskeie interessante punte na vore oor die ontdekkingsproses. Dit is duidelik dat die karakterisering van katodestrale 'n proses was wat lank voor Thomson se werk begin is, en verskeie wetenskaplikes het belangrike bydraes gelewer. In watter sin kan dan gesê word dat Thomson die elektron ontdek het? Hy het immers nie die vakuumbuis uitgevind of katodestrale ontdek nie. Ontdekking is dikwels 'n kumulatiewe proses. Die erkende ontdekker lewer sekerlik belangrike bydraes, maar dikwels nadat fundamentele waarnemings gemaak is en hulpmiddels deur ander uitgevind is. Thomson was nie die enigste fisikus wat die lading-tot-massa-verhouding van katodestrale in 1897 gemeet het nie, en ook nie die eerste wat sy resultate bekend gemaak het nie. (Sien Pais 1986.) Maar Thomson het hierdie meting en (later) die meting van die lading van die deeltjies uitgevoer, en hy het die belangrikheid daarvan as 'n bestanddeel van gewone materie erken.

Draers van negatiewe elektrisiteit

Inleidend

Die eerste plek waar 'n liggaam aangetref is, was 'n baie uitgeputte buis [3] waardeur 'n elektriese ontlading deurloop. As 'n elektriese ontlading deur 'n baie uitgeputte buis gestuur word, gloei die kante van die buis met 'n lewendige groen fosforesensie. Dat dit te wyte is aan iets wat in reguit lyne van die katode afloop-die elektrode waar die negatiewe elektrisiteit die buis binnedring-kan op die volgende manier getoon word (die eksperiment is 'n eksperiment wat baie jare gelede deur sir William Crookes gemaak is [4]) : 'N Maltese kruis van dun mika word tussen die katode en die wande van die buis geplaas. [5] As die ontslag verby is, strek die groen fosforesensie nie meer oor die einde van die buis nie, net soos die kruis afwesig was. Daar is nou 'n goed gedefinieerde kruis in die fosforesensie aan die einde van die buis, die miskruis het 'n skaduwee gegooi en die vorm van die skaduwee bewys dat die fosforesensie te wyte is aan iets wat in reguit lyne van die katode af beweeg, 'n dun bord mica. Die groen fosforesensie word veroorsaak deur katodestrale [6] en daar was op 'n tyd hewige twis oor die aard van hierdie strale. Twee standpunte was algemeen: een, wat hoofsaaklik deur Engelse fisici ondersteun is, was dat die strale negatief geëlektrifiseerde liggame is wat met groot snelheid van die katode afgeskiet is, en die ander siening, wat deur die meerderheid Duitse natuurkundiges gehou is, was dat die strale is 'n soort eteriese vibrasie of golwe. [7]

Die argumente dat die strale negatief gelaaide deeltjies is, is hoofsaaklik dat dit deur 'n magneet op dieselfde manier as bewegende, negatief geëlektrifiseerde deeltjies afgebuig word. Ons weet dat sulke deeltjies, wanneer 'n magneet naby hulle geplaas word, deur 'n krag bewerk word waarvan die rigting reghoekig met die magnetiese krag is, en ook reghoekig in die rigting waarin die deeltjies beweeg. [8]

As die deeltjies dus horisontaal van oos na wes beweeg, en die magnetiese krag horisontaal van noord na suid, sal die krag wat op die negatief geëlektrifiseerde deeltjies inwerk vertikaal en afwaarts wees. [9]

As die magneet so geplaas word dat die magnetiese krag in die rigting waarin die deeltjie beweeg, is, sal laasgenoemde nie deur die magneet beïnvloed word nie.

Die volgende stap in die bewys dat katodestrale negatief gelaaide deeltjies is, was om aan te toon dat wanneer hulle in 'n metaalvat vasgevang word, hulle 'n lading negatiewe elektrisiteit afstaan. Dit is die eerste keer gedoen deur Perrin. [10] Hierdie eksperiment is afdoende gemaak deur die vangvat uit die pad van die strale te plaas en dit met behulp van 'n magneet daarin te buig toe die vaartuig negatief gelaai word. [11]

Elektriese afbuiging van die strale

Deur die vakuumbuis uit te put totdat daar slegs 'n buitengewoon klein hoeveelheid lug oor was om 'n geleier te maak, kon ek van hierdie effek ontslae raak en die elektriese afbuiging van die katodestrale verkry. [14] Hierdie afbuiging het 'n rigting wat dui op 'n negatiewe lading op die strale.

So word katodestrale deur beide magnetiese en elektriese kragte afgebuig, net soos negatief geëlektrifiseerde deeltjies sou wees.

Hertz het egter getoon dat katodepartikels 'n ander eienskap besit wat teenstrydig lyk met die idee dat dit stofdeeltjies is, want hy het gevind dat dit baie dun metaalvelde kan binnedring, bv. stukke goue blaar en produseer aansienlike helderheid op glas agter hulle. [15] Die idee van deeltjies so groot soos die molekules van 'n gas wat deur 'n vaste plaat gaan, was 'n ietwat verbysterende idee, [16] en dit het my gelei om die aard van die deeltjies wat die katodestrale vorm, nader te ondersoek.

Die beginsel van die metode wat gebruik word, is soos volg: Wanneer 'n deeltjie met 'n lading e met snelheid v oor die kraglyne in 'n magnetiese veld beweeg, geplaas sodat die lyne van magnetiese krag reghoekig is met die beweging van die deeltjie , dan, as H die magnetiese krag is, sal die bewegende deeltjie inwerk deur 'n krag gelyk aan Hev. Hierdie krag werk in die rigting wat reghoekig is op die magnetiese krag en in die rigting van die beweging van die deeltjie. As ons ook 'n elektriese veld van krag X het, sal die katodestraal deur 'n krag Xe inwerk. As die elektriese en magnetiese velde so gerangskik is dat dit mekaar opponeer, dan, wanneer die krag Hev as gevolg van die magnetiese veld aangepas word om die krag as gevolg van die elektriese veld Xe te balanseer, sal die groen stuk fosforesensie as gevolg van die katodestrale tref die einde van die buis sal ongestoord wees, en ons het

As ons dus die waardes van X en H meet, soos ons sonder moeite kan doen, as die strale nie afgebuig word nie, kan ons die waarde van v, die snelheid van die deeltjies, bepaal. [17] In 'n baie uitgeputte buis kan dit 1 /3 die snelheid van lig wees, of ongeveer 60.000 myl per sekonde in buise wat nie so baie uitgeput is nie, dit mag nie meer as 5.000 myl per sekonde wees nie, maar in alle gevalle wanneer die katodestrale geproduseer word in buise is hul snelheid baie groter as die snelheid van enige ander bewegende liggaam waarmee ons kennis dra. Dit is byvoorbeeld duisende maal die gemiddelde snelheid waarmee die waterstofmolekules by gewone temperature beweeg, of inderdaad by enige temperatuur wat nog besef word. [18]

Bepaling van e/m

Dus is die verplasing van die stuk fosforesensie waar die strale die glas tref gelyk aan

Die resultate van die bepaling van die waardes van e / m wat deur hierdie metode gemaak is, is baie interessant, want daar word gevind dat, alhoewel die katodestrale geproduseer word, ons altyd dieselfde waarde van e / m kry vir al die deeltjies in die strale . Ons kan byvoorbeeld deur die vorm van die afvoerbuis en die druk van die gas in die buis te verander, groot veranderinge in die snelheid van die deeltjies veroorsaak, maar tensy die snelheid van die deeltjies so groot word dat hulle amper beweeg vinnig as lig, as ander oorwegings in ag geneem moet word, is die waarde van e / m byna konstant. [20] Die waarde van e / m is nie net onafhanklik van die snelheid nie. Wat nog meer merkwaardig is, is dat dit onafhanklik is van die soort elektrodes wat ons gebruik en ook van die soort gas in die buis. Die deeltjies wat die katodestrale vorm, moet afkomstig wees van die gas in die buis of van die elektrodes, maar ons kan enige soort stof gebruik asb vir die elektrodes en die buis vul met gas van enige aard en tog die waarde van e / m sal onveranderd bly. [21]

Hierdie konstante waarde, wanneer ons e / m meet in die c.g.s. stelsel van magnetiese eenhede, is gelyk aan ongeveer 1,7x10 7. As ons dit vergelyk met die waarde van die verhouding tussen die massa en die lading van elektrisiteit wat deur 'n voorheen bekende stelsel gedra word, vind ons dat dit van 'n heel ander orde is. Voordat die katodestrale ondersoek is, was die gelaaide waterstofatoom in die elektrolise van vloeistowwe die stelsel wat die grootste bekende waarde van e / m gehad het, en in hierdie geval is die waarde slegs 104, dus vir die liggaam in die katode strale die waarde van e / m is 1,700 keer die waarde vir die ooreenstemmende hoeveelheid vir die gelaaide waterstofatoom. Hierdie teenstrydigheid moet op een of ander manier ontstaan, óf die massa van die liggaam moet baie klein wees in vergelyking met die van die waterstofatoom, wat tot onlangs die kleinste massa in die fisika was, óf die lading op die liggaam baie groter as die op die waterstofatoom. Nou is dit bewys deur 'n metode wat ek kortliks sal beskryf, dat die elektriese lading in die twee gevalle feitlik dieselfde is, daarom word ons tot die gevolgtrekking gekom dat die massa van die liggaam slegs ongeveer 1/1,700 van die waterstof is atoom. Die atoom is dus nie die uiteindelike grens vir die onderverdeling van materie nie; ons kan verder gaan en by die liggaam kom, en in hierdie stadium is die liggaam dieselfde uit watter bron dit ook al kom.

Korpusse baie wyd versprei

Korpusse word ook uitgegee deur metale en ander liggame, maar veral deur die alkalimetale, wanneer dit aan lig blootgestel word. [23]

Dit word voortdurend in groot hoeveelhede uitgegee en met baie groot snelhede deur radioaktiewe stowwe soos uraan en radium [24] word dit in groot hoeveelhede geproduseer wanneer soute aan die brand gesteek word, en daar is goeie rede om aan te neem dat liggaamshonde ons bereik vanaf die son.

Die korpuskel is dus baie wyd versprei, maar waar dit ook al voorkom, behou dit sy individualiteit, e / m is altyd gelyk aan 'n sekere konstante waarde.

Dit lyk asof die liggaam onder die mees uiteenlopende omstandighede 'n deel vorm van allerhande materie, daarom lyk dit natuurlik dat dit as een van die stene waaruit atome opgebou word, beskou. [25]

Omvang van die elektriese lading wat deur die liggaam vervoer word

As gelaaide deeltjies in die gas voorkom, het Wilson getoon dat 'n veel kleiner hoeveelheid verkoeling voldoende is om die mis te produseer, 'n viervoudige oorversadiging is alles wat nodig is wanneer die gelaaide deeltjies die is wat in 'n gas voorkom wanneer dit in is 'n toestand waarin dit elektrisiteit gelei. Elke van die gelaaide deeltjies word die middelpunt waarin 'n druppel water die druppels vorm, 'n wolk, en dus word die gelaaide deeltjies, hoe klein hulle ook al is, nou sigbaar en kan waargeneem word.

Die effek van die gelaaide deeltjies op die vorming van 'n wolk kan baie duidelik getoon word deur die volgende eksperiment:

'N Vaartuig wat met water in aanraking kom, is by die temperatuur van die kamer met vog versadig. Hierdie vaartuig kommunikeer met 'n silinder waarin 'n groot suier op en af ​​gly. Die suier is aanvanklik bo -aan sy reis deur die lug skielik onder die suier uit te put, die lug in die vaartuig sal baie vinnig uitbrei. As lug egter uitbrei, word dit koel, dus is die lug in die vate wat voorheen versadig is, nou oorversadig. As daar geen stof teenwoordig is nie, sal daar geen neerslag van vog plaasvind nie, tensy die lug tot so 'n lae temperatuur afgekoel word dat die hoeveelheid vog wat nodig is om dit te versadig slegs ongeveer 1/8 daarvan is.

Die hoeveelheid verkoeling, en dus van oorversadiging, hang af van die beweging van die suier, hoe groter die reis, hoe groter die verkoeling. Gestel die reis word so gereguleer dat die oorversadiging minder as agtvoudig en groter as viervoudig is. Ons bevry nou die lug van stof deur wolk na wolk in die stowwerige lug te vorm terwyl die wolke val, dra hulle die stof saam met hulle, net soos in die natuur deur reën. Ons vind uiteindelik dat wanneer ons die uitbreiding maak, geen wolk sigbaar is nie. [28]

Die gas word nou in 'n geleidende toestand gemaak deur 'n bietjie radium naby die vaartuig te bring, dit vul die gas met groot hoeveelhede positief en negatief geëlektrifiseerde deeltjies. By die uitbreiding word 'n buitengewoon digte wolk gevorm. Dat dit te wyte is aan die elektrifisering van die gas, kan deur die volgende eksperiment aangetoon word:

Langs die binnemure van die vaartuig het ons twee vertikale geïsoleerde plate wat geëlektrifiseer kan word. As hierdie plate gelaai is, sleep hulle die geëlektrifiseerde deeltjies so vinnig as wat hulle gevorm word uit die gas, sodat ons op hierdie manier die aantal geëlektrifiseerde deeltjies in die gas kan ontslae raak of in elk geval grootliks kan verminder. As die uitbreiding nou gemaak word met die plate gelaai voordat die radium opgeneem word, word daar slegs 'n klein wolk gevorm. [29]

Ons kan die druppels gebruik om die lading op die deeltjies te vind, want as ons die suier se beweging ken, kan ons die hoeveelheid oorversadiging aflei, en dus die hoeveelheid water wat neergelê word wanneer die wolk vorm. Die water word gedeponeer in die vorm van 'n aantal klein druppels van dieselfde grootte, dus is die aantal druppels die volume van die water wat gedeponeer word gedeel deur die volume van een van die druppels. As ons dus die volume van een van die druppels vind, kan ons die aantal druppels vind wat rondom die gelaaide deeltjies gevorm word. As die deeltjies nie te veel is nie, het elkeen 'n druppel om dit, en ons kan dus die aantal geëlektrifiseerde deeltjies vind. [30]

Uit die tempo waarteen die druppels stadig val, kan ons die grootte daarvan bepaal. As gevolg van die viskositeit of wrywing van die lug val klein liggame nie met 'n voortdurend versnelde snelheid nie, maar bereik hulle gou 'n spoed wat uniform bly vir die res van die val, hoe kleiner die liggaam hoe stadiger hierdie spoed. Sir George Stokes het getoon dat v, die snelheid waarmee 'n druppel reën val, deur die formule gegee word

As ons die waardes van g en & mu vervang, kry ons

Ons kan op hierdie manier die volume van 'n druppel vind en kan dus, soos hierbo verduidelik, die aantal druppels en dus die aantal geëlektrifiseerde deeltjies bereken.

Dit is eenvoudig om die totale hoeveelheid elektrisiteit op hierdie deeltjies deur elektriese metodes te bepaal, en daarom kan ons, soos ons die aantal deeltjies ken, dadelik die lading op elke deeltjie aflei.

Dit was die metode waarmee ek eers die lading op die deeltjie bepaal het [31] HA Wilson het sedertdien 'n eenvoudiger metode gebruik wat op die volgende beginsels gebaseer is: CTR Wilson het getoon dat die waterdruppels makliker op negatief geëlektrifiseerde deeltjies kondenseer as op positief geëlektrifiseerde. Deur die uitbreiding aan te pas, is dit dus moontlik om druppels water om die negatiewe deeltjies te kry en nie die positiewe met hierdie uitbreiding nie, daarom word al die druppels negatief geëlektrifiseer. The size of these drops and therefore their weight can, as before, be determined by measuring the speed at which they fall under gravity. Suppose now, that we hold above the drops a positively electrified body then, since the drops are negatively electrified, they will be attracted towards the positive electricity, and thus the downward force on the drops will be diminished and they will not fall so rapidly as they did when free from electrical attraction. If we adjust the electrical attraction so that the upward force on each drop is equal to the weight of the drop, the drops will not fall at all, but will, like Mahomet's coffin[32], remain suspended between heaven and earth. If then we adjust the electrical force until the drops are in equilibrium and neither fall nor rise, we know that the upward force on each drop is equal to the weight of the drop, which we have already determined by measuring the rate of fall when the drop was not exposed to any electrical force. If X is the electrical force, e the charge on the drop, and w its weight, we have, when there is equilibrium,

It might be objected that the charge measured in the preceding experiments is the charge on a molecule or collection of molecules of the gas, and not the charge on a corpuscle.[33]

This objection does not, however, apply to another form in which I tried the experiment, where the charges on the corpuscles were got, not by exposing the gas to the effects of radium, but by allowing ultraviolet light to fall on a metal plate in contact with the gas. In this case, as experiments made in a very high vacuum show, the electrification, which is entirely negative, escapes from the metal in the form of corpuscles. When a gas is present, the corpuscles strike against the molecules of the gas and stick to them.

Thus, though it is the molecules which are charged, the charge on a molecule is equal to the charge on a corpuscle, and when we determine the charge on the molecules by the methods I have just described, we determine the charge carried by the corpuscle.

The value of the charge when the electrification is produced by ultraviolet light is the same as when the electrification is produced by radium.[34]

We have just seen that e , the charge on the corpuscle, is in electromagnetic units equal to 10 -20 , and we have previously found that e/m , m being the mass of a corpuscle, is equal to 1.7x10 7 , hence m = 6x10 -28 grammes.

We can realize more easily what this means if we express the mass of the corpuscle in terms of the mass of the atom of hydrogen.

We have seen that for the corpuscle e/m = 1.7x10 7 . If E is the charge carried by an atom of hydrogen in the electrolysis of dilute solutions, and M is the mass of the hydrogen atom, E/M = 10 4 hence e/m = 1,700 E/M .

We have already stated that the value of e found by the preceding methods agrees well with the value of E which has long been approximately known. Townsend has used a method in which the value of e/E is directly measured, and has shown in this way also that e equal to E . Hence, since e/m = 1,700 E/M , we have M = 1,700 m , i.e., the mass of a corpuscle is only about 1/1,700 part of the mass of the hydrogen atom.[35]

In all known cases in which negative electricity occurs in gases at very low pressures, it occurs in the form of corpuscles, small bodies with an invariable charge and mass. The case is entirely different with positive electricity.[36]

Notas

[2]Both of these properties of electrons, their very low mass and their widespread occurrence, had profound effects on scientists' understanding of matter. The small mass indicated that pieces of matter existed which were smaller (lighter) than the smallest atom yet known by a factor of 1000. The formation of the same small particles from a wide variety of sources suggested that those particles were common constituents of atoms, and not an exotic form of matter. The two conclusions taken together imply that even the smallest atoms have component parts, that they are not structureless or indivisible. (The picture of structureless atoms as the basic building blocks of atoms was rather widely, but by no means universally held at the close of the 19 th century. Some scientists, including Thomson, believed that atoms had structure, whether or not they were divisible. And a minority still regarded atoms themselves as unproved or as useful fictions.)

[3] Exhausted is used here in the sense of evacuated , that is, a glass tube from which the gas had been pumped. Vacuum tube would be another appropriate term for such a device.

[4]William Crookes was a productive researcher and highly original and speculative thinker in many areas of physics and chemistry. (See chapter 14, note 29.) His work on electrical discharges in vacuum tubes in the late 1870s laid some foundational work on which Thomson built indeed, his "Crookes tubes" were widely used in cathode ray research.

[5]See photo of Crookes' Maltese cross tube (at the Science Museum, London). A Maltese cross has arms of equal length and is flared at the ends. The cross was used as a heraldic symbol of the medieval crusading Knights of Malta. The advantage of employing this shape in the present experiment is that it is simple enough to fashion, yet complex enough to throw quite distinctive shadows. Mica is an aluminum silicate mineral readily split into thin transparent sheets.

[6]Cathode rays were known for much of the 19 th century. Descriptions of electrical discharges in partially evacuated containers date to the late 18 th century. Productive study of the rays began in the 1850s, when Johann Geissler improved the vacuum pump and vacuum tubes and Julius Plücker made systematic observations using those tubes. Eugen Goldstein coined the term cathode rays in 1876. They were called cathode rays because they were emitted from the cathode of the vacuum tube. The term cathode ray is obsolete today the rays would be described as a beam of electrons. See Anderson 1964 or Pais 1986 for detailed chronologies of cathode ray research.

Even though one rarely hears of cathode rays anymore, cathode ray tubes (CRTs) were specialized and sophisticated versions of vacuum tubes widely used for video display in television sets, computer monitors, oscilloscopes, and other devices throughout the second half of the 20th century. CRTs shoot electrons at a screen coated with phosphors, which glow when they are struck by the electron beam. (Thomson's tube glowed green because of the kind of glass it was made of other materials glow other colors when struck by electrons.) CRTs use magnetic fields to make the electron beam rapidly scan the tube to produce an image. (In the mid-19 th century, Plücker noticed that magnetic fields distort the glow of cathode rays.) Big projection screen TVs and flat-screen monitors have largely displaced CRTs for video monitors in the 21st century.

[7]The two alternatives represent two main categories of physical reality. The key word in the first alternative, suggested in 1871 by Cromwell Varley, is bodies . That is, the English physicists thought cathode rays were a stream of fast-moving particles and therefore matter. The key word in the second alternative, proposed in 1880 by Goldstein, is waves . That is, the German physicists thought cathode rays were a wave phenomenon, perhaps something like light and other related electromagnetic energy. At the end of the 19 th century, physicists considered waves and particles two distinct alternatives something could not be both a wave and a particle. The sharp distinction between waves and particles blurred during the first quarter of the 20 th century now physicists routinely refer to wavelike properties of particles and particle-like properties of waves. In fact, the electron turned out to be a particle which is involved in several wave-like phenomena (but that's another story).

[8]Thomson's line of argument, essentially, is that one can tell cathode rays are charged particles because they behave the way charged particles behave. The behavior of charged particles in magnetic fields is just one of several consequences that can be inferred from the hypothesis that cathode rays consist of charged particles.

There is a deep connection between electricity and magnetism, despite their seeming at first to be distinct phenomena. The fact that magnetic fields can deflect moving electrical charges is one of the manifestations of this deep connection. A more practical aspect of the relationship between electricity and magnetism is that moving electric charges can give rise to magnetic fields, and changing magnetic fields can set electric charges into motion. This connection is the basis for the generation of electrical current at power plants and for the design of electrical motors. The English scientists Michael Faraday (1791-1867) and James Clerk Maxwell (1831-1879 see portrait in Early History of Radio Astronomy, Frank D. Ghigo, National Radio Astronomy Observatory) were instrumental in unraveling the connections between electricity and magnetism.

[9]The diagram below shows the directions involved: down is into the screen and up is out of the screen.

[10]Jean Baptiste Perrin (1870-1942 see photo and biographical information at the Nobel Foundation website) carried out this collection of cathode rays in 1895 [Perrin 1895]. Perrin was awarded the Nobel Prize in physics in 1926 for his work on the random motion of atoms (known as Brownian movement), which he began in 1908.

[11]Thomson has so far described two independent lines of evidence to support the hypothesis that cathode rays are particles that carry a negative electrical charge. First, cathode rays exposed to a magnetic field act just like negative electric charges in motion would act. Second, a metal bombarded by cathode rays acquires a negative electrical charge. Thomson himself made the collection experiment conclusive and particularly elegant, by combined both lines of evidence (using magnetic deflection to guide the particles onto the metal collector) [Thomson 1897a, 1897b].

[12]If cathode rays are electrically charged particles, they should behave like charged particles in all respects in particularly, they ought to be deflected when exposed to an electric field. In 1883, German physicist Heinrich Hertz looked for deflection of cathode rays by electric fields but found no deflection.

Hertz (1857-1894 see photo in Early History of Radio Astronomy, Frank D. Ghigo, National Radio Astronomy Observatory) is best known for his work demonstrating the existence of electromagnetic waves, in particular radio waves. The frequencies of radio waves are measured in units named after him one hertz is one cycle per second. Frequencies in the FM band are in the neighborhood of 100 megahertz (millions of hertz), and AM frequencies are in the neighborhood of 1000 kilohertz (thousands of hertz).

[13]Thomson said that the passage of cathode rays made the gas in the tube capable of conducting electricity. A modern scientist would say that the cathode rays (electrons) ionize the gas molecules, breaking off additional electrons from the atoms and leaving positively charged ions . (Ions are electrically charged atoms or molecules.) Indeed, Thomson presented this picture of ionization in 1899, not long after his characterization of cathode rays.

Electrostatic attraction would cause the ions to surround the electrons. Since each of the charged particles itself gives rise to an electric field, it was certainly plausible to think that an external electric field would hardly be felt by the surrounded cathode rays. If Thomson was right (and he was), his next task would be to reduce the screening effect of the ions or otherwise prove that their interference prevented electric deflection of the cathode rays. If not, the failure of electric deflection experiments could be interpreted as evidence against the idea that cathode rays were electrically charged particles.

[14]The demonstration that cathode rays were deflected by electric fields awaited a technological development, improvement in the techniques for achieving high vacua (extremely low pressures). As Thomson later recalled [Thomson 1936]:

[15]I find it somewhat curious that Thomson fails to mention the student of Hertz who was awarded the Nobel Prize in physics one year before Thomson for his own work on cathode rays. Philipp Lenard (1862-1947 1897b].

[16]At the time of Hertz' experiments, those who thought that cathode rays were charged particles had in mind charged gas molecules. Since gas molecules were known to be incapable of penetrating metal foils, no wonder this observation was "startling." The observation would be somewhat less startling if the rays were supposed to be particles much smaller than gas molecules.

[17]The design of this experiment illustrates an elegant indirect measurement and the use of mathematical formalism to derive inferences from observations. The measurement is indirect in that it determines the speed of the particle without measuring either distance or time. (Indeed, Thomson tried a more direct measurement of cathode ray velocity in 1894 [Thomson 1894], but it turned out to be unreliable.) The force a magnetic field exerts on a charged particle is proportional to the speed of the particle as well as its charge thus, if that force could be measured the speed could be inferred. Thomson couldn't even quite measure the force, but he could arrange to balance the force with an electric field. Since the cathode rays made the glass tube glow where they hit it, the rays provided a visible means to tell then the magnetic and electric forces were in balance. When they were in balance, the two forces were equal. Then a single step of elementary algebra turned a mathematical statement about two equal forces into a formula for the velocity of the ray. Since the electric and magnetic field strengths were known and controlled by the experimenter, the velocity could be computed.

The figure below (from Thomson 1897b) shows a diagram of the apparatus including the plates for applying an electric field and a scale at the right end to measure deflection of the beam.

[18]In emphasizing how fast the rays are compared to forms of matter then known, Thomson does not stress that the rays are slow compared to light. But this observation is another piece of evidence against the hypothesis that the rays are electromagnetic waves, for those waves travel at the speed of light.

[19]This measurement of the charge to mass ratio ( e / m ) of the electron is also indirect, and it illustrates even better than the measurement of velocity the utility of algebraic language to make inferences. To paraphrase, an electric field with strength X applied perpendicular to the line of direction of the cathode rays will make the rays fall a distance d over the course of a flight of length l (essentially the length of the tube). The distance the rays will fall is given by:

[20]It would not be surprising if e/m were found to be independent of speed, for neither the mass nor the charge of an ion depends on speed--at least for ordinary speeds. The fact that there were some variations in the mass of the electron near the speed of light, as documented by Walter Kaufmann's careful measurements published in 1901, was interesting and required explanation. That explanation (and the "other considerations" Thomson mentions here) came in 1905 with Albert Einstein's theory of special relativity. Kaufmann is worth mentioning in an account of the discovery of the electron because he used the very method described here by Thomson to measure e/m of cathode rays in 1897.

[21]Each kind of ion has its own characteristic charge to mass ratio, because each ion has a specific electrical charge and its own characteristic mass. For example, hydrogen ions (H + ) all carry a particular amount of charge and have a particular mass, resulting in a characteristic e / m ratio sodium ions (Na + ) carry the same charge as hydrogen ions, but have a greater weight, and therefore a smaller characteristic e / m ratio.

Thomson found that cathode rays always had the same e / m ratio, no matter what metals were used for the cathodes and no matter what gas was used in the tubes. Kaufmann concluded that the hypothesis that cathode rays were particles was inconsistent with this result. Thomson had already been convinced by the preceding evidence that the rays were particles as we will see, he took the constancy of e/m as evidence that the rays are fragments common to all the gases.

[22]Rubidium (Rb), sodium (Na), and potassium (K) are all in the same column in the periodic table, and belong to the family of alkali metals. So it is not surprising that they have similar properties. In fact, one of the characteristics of that column of the table is the relative ease with which those atoms lose a single electron.

[23]Thomson did not discover the thermoelectric and photoelectric phenomena he just mentioned ( i.e. , the phenomena in which particles are ejected from hot bodies or metals exposed to light). He did, however, show that the particles involved in these phenomena are the same as cathode rays [Thomson 1899].

[24]By the time of this address, the radioactive fragments which had been labeled &beta [Rutherford 1899] had already been identified as electrons.

[25]From his earliest characterization of cathode rays, Thomson argued that they were building blocks of atoms [Thomson 1897a], and he elaborated that idea considerably by the time of this address. As early as 1897, he suggested a link between the arrangement of electrons in atoms and the periodicity of atomic properties [Thomson 1897b] (albeit not the link generally recognized today). In 1899 he proposed that ions, charged atoms, acquire their charge by the detachment and attachment of electrons [Thomson 1899]. In 1904 he attempted to explain atomic spectra in terms of the oscillations of electrons in atoms [Thomson 1904]. And in 1906 he argued that the number of electrons in an atom was of the same order of magnitude as its atomic weight (not thousands of electrons per atom, as had been thought up to that point) [Thomson 1906a]. Helge Kragh argues convincingly that Thomson believed that atoms were made up of some sort of corpuscle long before 1897. [Kragh 1997] It is therefore not surprising that Thomson was so prepared to identify the newly characterized cathode particles as one of the constituents of atoms and to construct structural models based on them.

[26]Scottish physicist Charles Thomson Rees Wilson (1869-1959 see biographical sketch at Nobel Foundation) was awarded the Nobel Prize in physics in 1927 for his invention and further development of the cloud chamber (which Thomson describes in some detail here). Wilson was a student of Thomson. He developed the tool for measuring the charge on ions produced by X-rays.

In this brief address, Thomson has mentioned two instances of how the development of tools allowed his research to progress: the cloud chamber and vacuum technology. Technology frequently does assist the progress of science in this way, even if the opposite relationship, the role of science in advancing technology, is more widely known.

[27]Keep in mind that Thomson worked in England he was very familiar with the phenomena of fog and rain!

[28]The process of rapid expansion cools the moist air. If any dust is present, tiny droplets will form on the dust particles, and carry them to the bottom of the container. The expansion (cooling) is repeated until all the dust has settled at the bottom of the container, carried down by droplets.

[29]When radium, a radioactive element which can ionize (electrify) the air, is introduced, a dense "cloud" is observed to form in dust-free air. Thomson asserts that the cloud is due to the presence of charged particles. How does he know? He can remove the charged particles, and when he does, he greatly reduces the extent of cloud formation.

[30]Now the experiment passes from the qualitative to the quantitative. So far, Thomson has explained how the cloud chamber can be used to detect and visualize charged particles: the visible droplet which forms in dust-free air is like a tag on the invisible charged particle. But the technique can provide even more information: by carefully controlling the amount of supersaturation, one can figure out how much water is contained in the "cloud" droplets by measuring the speed at which the droplets fall, one can compute the size of the droplets this information allows computation of the number of droplets. The assumption, as yet unstated but addressed below, is that the number of droplets is the same as the number of charged particles.

[31]From the number of particles and the total charge (obtained from other electrical measurements), one can determine the charge per particle. Thomson made this determination in 1899 [Thomson 1899].

[32]According to a European legend foreign to Islamic tradition, the coffin of the prophet Mohammad (Mahomet) was suspended by magnets in the middle of his tomb. Apparently this story was well enough known in England that figures as different as Thomson just after the 19 th century and Mary Wollstonecraft just before it ( Vindication of the Rights of Woman , 1792) could refer to it in such a casual way.

[33]Once again Thomson raises possible objections to his experiments and answers them. Here the question is how he knew that the droplets were forming on single charged particles rather than clusters of them, and how he knew the charge was that of an electron rather than an ionized gas molecule.

[34]In fact, the charge of the electron is a fundamental unit of electrical charge. It turns out that the positive building block of atoms, the proton, has the same amount of charge but with the opposite sign. The charges of ions are whole-number multiples of this fundamental charge.

[35]Here Thomson concludes the proof of the argument he made above: the very large e/m of the electron is due to an ordinary charge and a very small mass, much smaller than that of the lightest atom.

[36]Thomson's specialty was the conduction of electricity through gases. The electricity was carried by particles of negative charge and also by particles of positive charge. In gases, the negative charges were all alike (electrons), but the positive charges varied in mass and charge depending on (among other things) what gas was present. These positive ions are what is left of an atom or molecule of the gas after one or more electrons are removed.


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Kosten für den internationalen Versand

Sie finden die geschätzten Versandkosten für jedes eBay-Angebot im Abschnitt Versand und Zahlungsmethoden. Dort sehen Sie auch, welchen Versandservice der Verkäufer verwendet, von wo der Artikel verschickt wird und in welche Länder der Verkäufer seine Artikel verschickt.

Die Angebote enthalten gegebenenfalls auch Informationen zu den Zollgebühren und Einfuhrabgaben. Die endgültigen Kosten für ein Angebot stehen erst dann fest, wenn Sie den Artikel bei der Kaufabwicklung bezahlen. Wenn Sie z. B. während der Kaufabwicklung Ihre Lieferadresse ändern oder die geltenden Einfuhrregeln vor Ablauf der Zahlung geändert werden, können sich auch die Gebühren ändern.

Wenn Sie die Versanddetails bei der Kaufabwicklung vor der Bezahlung bestätigen, sehen Sie die endgültigen Kosten.


令和2年度PTA総会は、新型コロナウイルスの感染拡大防止という観点から、書面審議にさせていただくことにいたします。 つきましては、議案書を生徒にお渡ししましたので、御覧いただき、「【甲府西高等学校PTA総会】書面審査フォーム」から御意見等を入力いただきますようお願い申し上げます。 上記の青字部分をクリックして、「書面審査フォーム」に進んでください。 &nb.

来年度の前期募集に関する情報をホームページに掲載しました。 詳しくは 前期募集について をご覧ください。

生徒並びに保護者の皆様へ 2020/5/26 8:30 更新 5月25日(月)より学校が再開となりましたが、学校の出欠席の取り扱いにつきましては、発熱や風邪の症状等がある場合の欠席は出席停止とするなど、新型コロナウィルス感染拡大防止のための柔軟な措置が求められております。 そこで、当面の間、本校では以下の事由による欠席につきまし.

生徒・保護者の皆様へ 2020/05/20 19:15 更新 緊急事態宣言が解除されたとはいえ、新型コロナウィルス感染拡大防止に向けては、依然として感染予防に努めた行動が求められております。県教育委員会は、予定どおり5月25日から学校を再開するとしておりますが、5月中は分散登校を、少なくとも6月の第1週は時差登校を、との方針を示しております.

生徒・保護者の皆様へ 2020/5/15 17:45 更新 5月11日・12日の課題提出や教材配付に関する登校につきまして、御理解と御協力をありがとうございました。オンラインによる指導にも努めておりますが、直接生徒の皆さんと会うことができ、気持ちも落ち着いたところです。今回の登校が一つのきっかけとなり、生徒の皆さんも少しでも前向きな気持ちにな.

5月24日まで休校が延長されました。 その間の学習の重点事項について再度紹介します。 今までと同様に該当の年次、教科を選択して指示に従ってください。 学校再開後の学習にもスムーズに授業が行えるよう、皆さん学習に励んでください。 本校の先生方による動画ですが、Teamsに移行します。 教科によってはYoutubeも併用するところも.

生徒並びに保護者の皆様へ 2020/5/8 18:45 更新 臨時休業期間が再び延長されまたことを受け、本校では、これまでの基本方針に基づく取組を引き続き進めながら、生徒の皆さんの学習や生活面の支援をしていきます。先の見通しがもてない状況にはありますが、生徒の皆さんが目標をもちながら、自分のできることに集中し、有意義な日々が過ごせていけますようサ.

保護者の皆様へ 2020/5/7 18:15 更新 臨時休業が長引いており、保護者の皆様には何かと御心労をおかけしておりますが、本校の対応につきまして、御理解と御協力をいただいておりますことに厚く感謝申しあげます。 さて、先日、今年度のPTA総会につきまして、御連絡をさせていただきましたが、学校再開が.

生徒及び保護者の皆様へ 2020/5/7 17:30 更新 学習や生活状況の確認、課題の提出や新たな教材の配付などを目的として、以下の日程での分散登校を実施します。短時間であること、一人一人の距離を保つこと、アルコール消毒の徹底など、感染予防には十分配慮いたしますので、趣旨を御理解のうえ、御協力をよろしくお願いいたします。 -登.


Symbol on utility pole in photograph from 1906 - History

CleopatraCleopatra VII Philopator was the last active ruler of the Ptolemaic Kingdom of Egypt. As a member of the Ptolemaic dynasty, she was a descendant of its founder Ptolemy I Soter, a Macedonian Greek general and companion of Alexander the Great. After the death of Cleopatra, Egypt became a province of the Roman Empire, marking the end of the second to last Hellenistic state and the age that had lasted since the reign of Alexander. Her native language was Koine Greek, and she was the only Ptolemaic ruler to learn the Egyptian language.

BibleThe Bybel is a collection of religious texts or scriptures sacred to Christians, Jews, Samaritans, Rastafari and others. It appears in the form of an anthology, a compilation of texts of a variety of forms that are all linked by the belief that they are collectively revelations of God. These texts include theologically-focused historical accounts, hymns, prayers, proverbs, parables, didactic letters, erotica, poetry, and prophecies. Believers also generally consider the Bible to be a product of divine inspiration.

BridgertonBridgerton is an American streaming television period drama series created by Chris Van Dusen and produced by Shonda Rhimes. It is based on Julia Quinn's novels set in the competitive world of Regency era London's Ton during the season, when debutantes are presented at court. It premiered on Netflix on December 25, 2020.

Donald TrumpDonald John Trump is the 45th and current president of the United States. Before entering politics, he was a businessman and television personality.

Regé-Jean PageRegé-Jean Page is a Zimbabwean and English actor. He is known for playing Chicken George in the 2016 miniseries Wortels and from 2018 to 2019 was a regular cast member on the ABC legal drama For the People. As of 2020, Page stars in the Netflix period drama, Bridgerton as Simon Basset, Duke of Hastings.

Ashley BidenAshley Blazer Biden is an American social worker, activist, philanthropist, and fashion designer. The daughter of U.S. President Joe Biden and First Lady Jill Biden, she served as the executive director of the Delaware Center for Justice from 2014 to 2019. Prior to her administrative role at the center, she worked in the Delaware Department of Services for Children, Youth, and Their Families. Biden founded the fashion company Livelihood, which partners with the online retailer Gilt Groupe to raise money for community programs focused on eliminating income inequality in the United States, launching it at New York Fashion Week in 2017.

Rachel LevineRachel L. Levine is an American pediatrician who has served as the Pennsylvania Secretary of Health since 2017. She is a Professor of Pediatrics and Psychiatry at the Penn State College of Medicine, and previously served as the Pennsylvania Physician General from 2015 to 2017. She is one of only a handful of openly transgender government officials in the United States. President Joe Biden has nominated Levine to be Assistant Secretary for Health. She would be the first openly transgender federal official to be confirmed by the Senate.


Simbool op nutspaal op foto uit 1906 - Geskiedenis

CleopatraCleopatra VII Philopator was die laaste aktiewe heerser van die Ptolemaïese Koninkryk Egipte. As lid van die Ptolemaïese dinastie was sy 'n afstammeling van die stigter Ptolemaeus I Soter, 'n Masedoniese Griekse generaal en metgesel van Alexander die Grote. Na die dood van Cleopatra het Egipte 'n provinsie van die Romeinse Ryk geword, wat die einde was van die tweede tot laaste Hellenistiese staat en die tydperk wat sedert die bewind van Alexander geduur het. Haar moedertaal was Koine Grieks, en sy was die enigste Ptolemaïese heerser wat die Egiptiese taal geleer het.

Bybel Die Bybel is 'n versameling godsdienstige tekste of geskrifte wat heilig is vir Christene, Jode, Samaritane, Rastafari en ander. Dit verskyn in die vorm van 'n bloemlesing, 'n samestelling van tekste van verskillende vorme wat almal verbind is deur die oortuiging dat dit gesamentlik openbarings van God is. Hierdie tekste bevat teologies gefokusde historiese verslae, gesange, gebede, spreuke, gelykenisse, didaktiese briewe, erotika, poësie en profesieë. Gelowiges beskou die Bybel ook oor die algemeen as 'n produk van goddelike inspirasie.

BridgertonBridgerton is 'n Amerikaanse dramareeks in die televisietydperk, geskep deur Chris Van Dusen en vervaardig deur Shonda Rhimes. Dit is gebaseer op romans van Julia Quinn in die mededingende wêreld van die Londense Regency -era Ton gedurende die seisoen, wanneer debutante by die hof aangebied word. Dit het op 25 Desember 2020 op Netflix verskyn.

Donald TrumpDonald John Trump is die 45ste en huidige president van die Verenigde State. Voordat hy die politiek betree het, was hy 'n sakeman en televisiepersoonlikheid.

Regé-Jean PageRegé-Jean Page is 'n Zimbabwiese en Engelse akteur. Hy is bekend daarvoor dat hy Chicken George in die 2016 -miniserie gespeel het Wortels en van 2018 tot 2019 was 'n gereelde rolspeler in die ABC -regsdrama Vir die mense. Vanaf 2020 speel Page in die drama van Netflix, Bridgerton as Simon Basset, hertog van Hastings.

Ashley BidenAshley Blazer Biden is 'n Amerikaanse maatskaplike werker, aktivis, filantroop en mode -ontwerper. Sy was die dogter van die Amerikaanse president, Joe Biden, en presidentsvrou Jill Biden, en was die uitvoerende direkteur van die Delaware Center for Justice van 2014 tot 2019. Voor haar administratiewe rol by die sentrum, werk sy in die departement van kinders in Delaware, Jeug en hul gesinne. Biden het die modeonderneming Livelihood gestig, wat saam met die aanlynkleinhandelaar Gilt Groupe geld insamel vir gemeenskapsprogramme wat daarop gemik is om inkomste -ongelykheid in die Verenigde State uit te skakel, en dit op die New York Fashion Week in 2017 bekendgestel.

Rachel LevineRachel L. Levine is 'n Amerikaanse kinderarts wat as die minister van gesondheid van Pennsylvania gedien het sedert 2017. Sy is 'n professor in kindergeneeskunde en psigiatrie aan die Penn State College of Medicine, en was voorheen die Pennsylvania Physician General van 2015 tot 2017. Sy is een van die enigste 'n handjievol openlik transgender regeringsamptenare in die Verenigde State. President Joe Biden het Levine aangewys as assistent -sekretaris vir gesondheid. Sy sou die eerste openlik transgender federale amptenaar wees wat deur die senaat bevestig is.


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