{"id":3328,"date":"2017-10-01T21:55:22","date_gmt":"2017-10-01T21:55:22","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=3328"},"modified":"2024-09-04T14:02:59","modified_gmt":"2024-09-04T14:02:59","slug":"eletromagnetismo-2017-2016-2015","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/vestibulares-recentes\/eletricidade\/eletromagnetismo-2017-2016-2015\/","title":{"rendered":"Eletromagnetismo \u2013 2017 \u2013 2016 – 2015"},"content":{"rendered":"

Vestibulares Recentes \u2013 Eletricidade<\/span><\/span><\/span><\/p>\n

Eletromagnetismo \u2013 2017 \u2013 2016 – 2015<\/span><\/span><\/span><\/p>\n

Im\u00e3s e campo magn\u00e9tico<\/span><\/span><\/span><\/p>\n

01-(COL\u00c9GIO NAVAL-015)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Com rela\u00e7\u00e3o aos\u00a0<\/b><\/span><\/span>conceitos de eletricidade e magnetismo<\/b><\/span><\/span>, coloque\u00a0<\/b><\/span><\/span>V (verdadeiro) ou F (falso)\u00a0<\/b><\/span><\/span>nas afirmativas abaixo e, em seguida,\u00a0<\/b><\/span><\/span>assinale a <\/b><\/span><\/span>op\u00e7\u00e3o<\/b><\/span><\/span>\u00a0que representa a\u00a0<\/b><\/span><\/span>sequ\u00eancia correta.<\/b><\/span><\/span><\/p>\n

( ) Na\u00a0<\/b><\/span><\/span>eletriza\u00e7\u00e3o por atrito<\/b><\/span><\/span>, o corpo\u00a0<\/b><\/span><\/span>perde el\u00e9trons\u00a0<\/b><\/span><\/span>passa a\u00a0<\/b><\/span><\/span>ter mais pr\u00f3tons do que possu\u00eda anteriormente<\/b><\/span><\/span>\u00a0e, nesse caso,\u00a0<\/b><\/span><\/span>fica eletrizado com carga positiva<\/b><\/span><\/span>.<\/b><\/span><\/span><\/p>\n

( )\u00a0<\/b><\/span><\/span>Condutores<\/b><\/span><\/span>\u00a0s\u00e3o corpos que facilitam a\u00a0<\/b><\/span><\/span>passagem da corrente el\u00e9trica, pois\u00a0<\/b><\/span><\/span>possuem grande quantidade de el\u00e9trons livres.<\/b><\/span><\/span><\/p>\n

( )\u00a0<\/b><\/span><\/span>Um im\u00e3<\/b><\/span><\/span>, em forma de barra, ao ser\u00a0<\/b><\/span><\/span>cortado ao meio<\/b><\/span><\/span>, d\u00e1 origem a\u00a0<\/b><\/span><\/span>dois novos im\u00e3s<\/b><\/span><\/span>,\u00a0<\/b><\/span><\/span>cada um com apenas um polo (norte ou sul).<\/b><\/span><\/span><\/p>\n

( ) A b\u00fassola magn\u00e9tica, cuja extremidade encarnada \u00e9 o seu polo norte, aponta para uma dire\u00e7\u00e3o definida da Terra, pr\u00f3ximo ao polo norte geogr\u00e1fico.<\/b><\/span><\/span><\/p>\n

( ) Geradores s\u00e3o dispositivos que transformam outras formas de energia em energia el\u00e9trica.<\/b><\/span><\/span><\/p>\n

( ) O chuveiro el\u00e9trico pode ser considerado um resistor pois transforma energia el\u00e9trica em energia exclusivamente t\u00e9rmica.<\/b><\/span><\/span><\/p>\n

(A) (F) (V) (F) (V) (V) (V)\u00a0<\/b><\/span><\/span><\/span><\/p>\n

(B)<\/b><\/span><\/span><\/span>\u00a0(F) (F) (V) (V) (F) (V)\u00a0<\/b><\/span><\/span><\/span><\/p>\n

(C)<\/b><\/span><\/span><\/span>\u00a0(V) (F) (F) (V) (V) (F)<\/b><\/span><\/span><\/span><\/p>\n

(D)<\/b><\/span><\/span>\u00a0(V) (V) (V) (F) (F) (F)\u00a0<\/b><\/span><\/span><\/p>\n

(E)<\/b><\/span><\/span>\u00a0(F) (V) (V) (F) (F) (V)<\/b><\/span><\/span><\/p>\n

02-(UFSC-SC-015)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A ideia de\u00a0<\/b><\/span><\/span>linhas de campo magn\u00e9tico<\/b><\/span><\/span>\u00a0foi introduzida pelo f\u00edsico e qu\u00edmico ingl\u00eas\u00a0<\/b><\/span><\/span>Michael Faraday<\/b><\/span><\/span>\u00a0(1791- 1867) para explicar os\u00a0<\/b><\/span><\/span>efeitos e a natureza do campo magn\u00e9tico<\/b><\/span><\/span>. Na figura abaixo, extra\u00edda do artigo \u201cPesquisas Experimentais em Eletricidade\u201d, publicado em 1852, Faraday\u00a0<\/b><\/span><\/span>mostra a forma assumida pelas linhas de campo com o uso de limalha de ferro espalhada ao redor deuma barra magn\u00e9tica<\/b><\/span><\/span>.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

Sobre\u00a0<\/b><\/span><\/span>campo magn\u00e9tico, \u00e9 CORRETO afirmar<\/b><\/span><\/span>\u00a0que:<\/b><\/span><\/span><\/p>\n

01.\u00a0<\/b><\/span><\/span>o\u00a0<\/b><\/span><\/span>vetor campo magn\u00e9tico<\/b><\/span><\/span>\u00a0em cada ponto\u00a0<\/b><\/span><\/span>\u00e9 perpendicular \u00e0 linha de campo magn\u00e9tico<\/b><\/span><\/span>\u00a0que passa por este ponto.<\/b><\/span><\/span><\/p>\n

02.\u00a0<\/b><\/span><\/span>as\u00a0<\/b><\/span><\/span>linhas de campo magn\u00e9tico<\/b><\/span><\/span>\u00a0s\u00e3o\u00a0<\/b><\/span><\/span>cont\u00ednuas<\/b><\/span><\/span>, atravessando a barra magn\u00e9tica.<\/b><\/span><\/span><\/p>\n

04.\u00a0<\/b><\/span><\/span>as\u00a0<\/b><\/span><\/span>linhas de campo magn\u00e9tico<\/b><\/span><\/span>\u00a0nunca se cruzam.<\/b><\/span><\/span><\/p>\n

08.\u00a0<\/b><\/span><\/span>por conven\u00e7\u00e3o, as linhas de campo magn\u00e9tico\u00a0<\/b><\/span><\/span>\u201csaem\u201d do polo sul e \u201centram\u201d no polo norte.<\/b><\/span><\/span><\/p>\n

16.\u00a0<\/b><\/span><\/span>as regi\u00f5es com\u00a0<\/b><\/span><\/span>menor densidade<\/b><\/span><\/span>\u00a0de linhas de campo magn\u00e9tico pr\u00f3ximas\u00a0<\/b><\/span><\/span>indicam um campo magn\u00e9tico mais intenso.<\/b><\/span><\/span><\/p>\n

32. quebrar um \u00edm\u00e3 em forma de barra<\/b><\/span><\/span>\u00a0\u00e9 uma maneira simples de obter <\/b><\/span><\/span>dois polos magn\u00e9ticos isolados.<\/b><\/span><\/span><\/p>\n

64. cargas el\u00e9tricas<\/b><\/span><\/span>\u00a0em repouso\u00a0<\/b><\/span><\/span>n\u00e3o\u00a0<\/b><\/span><\/span>interagem com o campo magn\u00e9tico.<\/b><\/span><\/span><\/p>\n

For\u00e7a\u00a0 magn\u00e9tica sobre uma carga m\u00f3vel imersa num campo magn\u00e9tico<\/span><\/span><\/span><\/p>\n

03-(UDESC-SC-016)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

04-(FGV.SP-017)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Uma part\u00edcula eletrizada\u00a0<\/b><\/span><\/span>de\u00a0<\/b><\/span><\/span>massa m\u00a0<\/b><\/span><\/span>gira no interior de um\u00a0<\/b><\/span><\/span>campo magn\u00e9tico uniforme\u00a0<\/b><\/span><\/span>descrevendo um\u00a0<\/b><\/span><\/span>movimento circular uniforme de raio R e frequ\u00eancia f.\u00a0<\/b><\/span><\/span>Ent\u00e3o um\u00a0<\/b><\/span><\/span>sistema de n part\u00edculas iguais a essa,\u00a0<\/b><\/span><\/span>girando nas\u00a0<\/b><\/span><\/span>mesmas condi\u00e7\u00f5es, estar\u00e1 dotado de uma energia cin\u00e9tica<\/b><\/span><\/span>\u00a0dada por<\/b><\/span><\/span><\/span><\/span><\/p>\n

(A)\u00a0<\/b><\/span><\/span>2.\"\"2.f2.n.m.R<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

(B)\u00a0<\/b><\/span><\/span>2.\"\"2.f2.n.m\/R<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

(C)\u00a0<\/b><\/span><\/span>2.\"\"2.f2.n\/m.R<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

(D)\u00a0<\/b><\/span><\/span>n.m\/2.\"\"2.f2.R<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

(E)\u00a0<\/b><\/span><\/span>n.m.R2\/2.\"\"2.f<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

 <\/p>\n

05-(UERJ-RJ-015)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Part\u00edculas de carga el\u00e9trica\u00a0<\/b><\/span><\/span>q\u00a0<\/b><\/span><\/span>e massa\u00a0<\/b><\/span><\/span>m<\/b><\/span><\/span>\u00a0penetram no plano horizontal de uma regi\u00e3o do espa\u00e7o na qual\u00a0<\/b><\/span><\/span>existe um campo magn\u00e9tico de intensidade <\/b><\/span><\/span>B, normal a esse plano<\/b><\/span><\/span>.<\/b><\/span><\/span>\u00a0Ao entrar na regi\u00e3o, as part\u00edculas s\u00e3o submetidas a um selecionador de velocidades que deixa passar apenas aquelas com <\/b><\/span><\/span>velocidade v<\/b><\/span><\/span>o<\/b><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/p>\n

Admita que, na\u00a0<\/b><\/span><\/span>regi\u00e3o do campo magn\u00e9tico, a trajet\u00f3ria<\/b><\/span><\/span>\u00a0descrita por uma das part\u00edculas selecionadas seja\u00a0<\/b><\/span><\/span>circular.<\/b><\/span><\/span><\/p>\n

Escreva a\u00a0<\/b><\/span><\/span>express\u00e3o matem\u00e1tica para o\u00a0<\/b><\/span><\/span>raio\u00a0<\/b><\/span><\/span>dessa trajet\u00f3ria em fun\u00e7\u00e3o de:<\/b><\/span><\/span><\/p>\n

\u2022\u00a0<\/span>massa, carga e velocidade da part\u00edcula;<\/b><\/span><\/span><\/p>\n

\u2022\u00a0<\/span>intensidade do campo magn\u00e9tico.<\/b><\/span><\/span><\/p>\n

06-(ENEM-MEC-016)<\/span><\/span><\/span><\/p>\n

\"\"
\n<\/b><\/span><\/span>A\u00a0<\/b><\/span><\/span>magnetohipertermia\u00a0<\/b><\/span><\/span>\u00e9 um\u00a0<\/b><\/span><\/span>procedimento terap\u00eautico<\/b><\/span><\/span>\u00a0que se\u00a0<\/b><\/span><\/span>baseia na eleva\u00e7\u00e3o da temperatura das c\u00e9lulas de uma regi\u00e3o espec\u00edfica<\/b><\/span><\/span>\u00a0do corpo <\/b><\/span><\/span>que estejam afetadas por um tumor.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Nesse\u00a0<\/b><\/span><\/span>tipo\u00a0<\/b><\/span><\/span>de\u00a0<\/b><\/span><\/span>tratamento, nanopart\u00edculas magn\u00e9ticas<\/b><\/span><\/span>\u00a0s\u00e3o\u00a0<\/b><\/span><\/span>fagocitadas <\/b><\/span><\/span>pelas\u00a0<\/b><\/span><\/span>c\u00e9lulas tumorais,<\/b><\/span><\/span>\u00a0e um\u00a0<\/b><\/span><\/span>campo magn\u00e9tico alternado externo \u00e9 utilizado para promover a agita\u00e7\u00e3o das nanopart\u00edculas e consequente aquecimento da c\u00e9lula.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>eleva\u00e7\u00e3o de temperatura descrita ocorre porque<\/b><\/span><\/span><\/span><\/span><\/p>\n

a)<\/b><\/span><\/span>\u00a0o\u00a0<\/b><\/span><\/span>campo magn\u00e9tico\u00a0<\/b><\/span><\/span>gerado pela\u00a0<\/b><\/span><\/span>oscila\u00e7\u00e3o das nanopart\u00edculas<\/b><\/span><\/span>\u00a0\u00e9 <\/b><\/span><\/span>absorvido pelo tumor.<\/b><\/span><\/span><\/span><\/span><\/p>\n

b)<\/b><\/span><\/span>\u00a0o campo\u00a0<\/b><\/span><\/span>magn\u00e9tico alternado faz as nanopart\u00edculas girarem, <\/b><\/span><\/span>transferindo\u00a0<\/b><\/span><\/span>calor por atrito.<\/b><\/span><\/span><\/span><\/span><\/p>\n

c)<\/b><\/span><\/span>\u00a0as\u00a0<\/b><\/span><\/span>nanopart\u00edculas interagem magneticamente<\/b><\/span><\/span>\u00a0com as\u00a0<\/b><\/span><\/span>c\u00e9lulas do corpo, <\/b><\/span><\/span>transferindo<\/b><\/span><\/span>\u00a0calor.<\/b><\/span><\/span><\/span><\/span><\/p>\n

d)<\/b><\/span><\/span>\u00a0o\u00a0<\/b><\/span><\/span>campo magn\u00e9tico alternado fornece calor<\/b><\/span><\/span>\u00a0para as\u00a0<\/b><\/span><\/span>nanopart\u00edculas que o transfere \u00e0s c\u00e9lulas\u00a0<\/b><\/span><\/span>do\u00a0<\/b><\/span><\/span>corpo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

e)<\/b><\/span><\/span>\u00a0as\u00a0<\/b><\/span><\/span>nanopart\u00edculas s\u00e3o aceleradas<\/b><\/span><\/span>\u00a0em um\u00a0<\/b><\/span><\/span>\u00fanico sentido em raz\u00e3o da intera\u00e7\u00e3o<\/b><\/span><\/span>\u00a0com o\u00a0<\/b><\/span><\/span>campo magn\u00e9tico<\/b><\/span><\/span>, fazendo-as\u00a0<\/b><\/span><\/span>colidir com as c\u00e9lulas e transferir calor<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

For\u00e7a magn\u00e9tica sobre um condutor retil\u00edneo imerso num campo magn\u00e9tico<\/span><\/span><\/span><\/p>\n

07-(UNICENTRO-PR-015)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um\u00a0<\/b><\/span><\/span>condutor retil\u00edneo<\/b><\/span><\/span>, pelo qual percorre uma\u00a0<\/b><\/span><\/span>corrente el\u00e9trica cont\u00ednua e constante<\/b><\/span><\/span>, est\u00e1 imerso em uma regi\u00e3o com\u00a0<\/b><\/span><\/span>campo magn\u00e9tico uniforme\"\".<\/b><\/span><\/span><\/p>\n

Assinale a\u00a0<\/b><\/span><\/span>alternativa que corresponde,\u00a0<\/b><\/span><\/span>corretamente<\/b><\/span><\/span>, \u00e0 figura que representa a a\u00e7\u00e3o da\u00a0<\/b><\/span><\/span>for\u00e7a magn\u00e9tica sobre o condutor nessa configura\u00e7\u00e3o.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

08-(UNESP-SP-017)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

 <\/p>\n

09-(AFA \u2013 015\/016)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span>lado EF<\/b><\/span><\/span>\u00a0de uma\u00a0<\/b><\/span><\/span>espira<\/b><\/span><\/span>\u00a0condutora quadrada indeform\u00e1vel, de\u00a0<\/b><\/span><\/span>massa m,<\/b><\/span><\/span>\u00a0\u00e9 preso a uma\u00a0<\/b><\/span><\/span>mola ideal<\/b><\/span><\/span>\u00a0e\u00a0<\/b><\/span><\/span>n\u00e3o condutora<\/b><\/span><\/span>, de\u00a0<\/b><\/span><\/span>constante el\u00e1stica K.<\/b><\/span><\/span><\/p>\n

Na\u00a0<\/b><\/span><\/span>posi\u00e7\u00e3o de equil\u00edbrio<\/b><\/span><\/span>, o\u00a0<\/b><\/span><\/span>plano da espira<\/b><\/span><\/span>\u00a0fica paralelo ao\u00a0<\/b><\/span><\/span>campo magn\u00e9tico B gerado por um \u00edm\u00e3<\/b><\/span><\/span>\u00a0em\u00a0<\/b><\/span><\/span>forma de U,<\/b><\/span><\/span>\u00a0conforme ilustra a figura abaixo.<\/b><\/span><\/span><\/p>\n

\"\"\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span>lado CD \u00e9 pivotado<\/b><\/span><\/span>\u00a0e pode\u00a0<\/b><\/span><\/span>girar\u00a0<\/b><\/span><\/span>livremente em torno do\u00a0<\/b><\/span><\/span>suporte S<\/b><\/span><\/span>, que \u00e9 <\/b><\/span><\/span>posicionado paralelamente\u00a0<\/b><\/span><\/span>\u00e0s linhas\u00a0<\/b><\/span><\/span>de indu\u00e7\u00e3o do campo magn\u00e9tico.<\/b><\/span><\/span><\/p>\n

Considere que a\u00a0<\/b><\/span><\/span>espira \u00e9 percorrida por uma corrente el\u00e9trica i,<\/b><\/span><\/span>\u00a0cuja <\/b><\/span><\/span>intensidade\u00a0<\/b><\/span><\/span>varia\u00a0<\/b><\/span><\/span>senoidalmente<\/b><\/span><\/span>, em fun\u00e7\u00e3o do\u00a0<\/b><\/span><\/span>tempo t,<\/b><\/span><\/span>\u00a0conforme indicado no gr\u00e1fico acima.<\/b><\/span><\/span><\/p>\n

Nessas condi\u00e7\u00f5es<\/b><\/span><\/span>,\u00a0<\/b><\/span><\/span>pode-se afirmar<\/b><\/span><\/span>\u00a0que a<\/b><\/span><\/span><\/p>\n

A)<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>espira<\/b><\/span><\/span>\u00a0oscilar\u00e1 em\u00a0<\/b><\/span><\/span>MHS,<\/b><\/span><\/span>\u00a0com frequ\u00eancia igual a\u00a0<\/b><\/span><\/span>1\/t<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span><\/p>\n

B)<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>espira\u00a0<\/b><\/span><\/span>permanecer\u00e1\u00a0<\/b><\/span><\/span>na sua posi\u00e7\u00e3o original de equil\u00edbrio<\/b><\/span><\/span><\/p>\n

C) mola<\/b><\/span><\/span>\u00a0apresentar\u00e1 uma\u00a0<\/b><\/span><\/span>deforma\u00e7\u00e3o m\u00e1xima dada por Bil\/mgK<\/b><\/span><\/span><\/p>\n

D)<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>mola\u00a0<\/b><\/span><\/span>apresentar\u00e1 uma\u00a0<\/b><\/span><\/span>deforma\u00e7\u00e3o m\u00e1xima<\/b><\/span><\/span>\u00a0dada\u00a0<\/b><\/span><\/span>por (Bil + mg)\/K<\/b><\/span><\/span><\/p>\n

Campo magn\u00e9tico originado por um condutor retil\u00edneo extenso \u2013 For\u00e7a de intera\u00e7\u00e3o entre dois fios condutores paralelos<\/span><\/span><\/span><\/p>\n

10-(PUC-SP-017)<\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Dois longos fios met\u00e1licos, retil\u00edneos e flex\u00edveis\u00a0<\/b><\/span><\/span>est\u00e3o inicialmente <\/b><\/span><\/span>dispostos conforme indica<\/b><\/span><\/span>\u00a0a\u00a0<\/b><\/span><\/span>Figura 1<\/b><\/span><\/span>\u00a0e\u00a0<\/b><\/span><\/span>localizados numa regi\u00e3o do espa\u00e7o onde h\u00e1 a presen\u00e7a de um intenso campo magn\u00e9tico constante e perpendicular ao plano da folha.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Quando os\u00a0<\/b><\/span><\/span>fios s\u00e3o percorridos por corrente el\u00e9trica de mesma intensidade constante<\/b><\/span><\/span>, verificam-se as\u00a0<\/b><\/span><\/span>deforma\u00e7\u00f5es indicadas na Figura 2.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Para que\u00a0<\/b><\/span><\/span>isso seja poss\u00edvel,\u00a0<\/b><\/span><\/span>o\u00a0<\/b><\/span><\/span>sentido do campo magn\u00e9tico<\/b><\/span><\/span>\u00a0e\u00a0<\/b><\/span><\/span>da corrente el\u00e9trica em cada fio\u00a0<\/b><\/span><\/span>deve ser:<\/b><\/span><\/span><\/span><\/span><\/p>\n

(A) Campo magn\u00e9tico entrando na folha (\u0425)\u00a0<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>sentido da corrente el\u00e9trica de A para B no fio 1\u00a0<\/b><\/span><\/span>e sentido de\u00a0<\/b><\/span><\/span>B para A no fio 2.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(B) Campo magn\u00e9tico saindo da folha (\u2022)\u00a0<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>sentido da corrente el\u00e9trica de A para B no fio 1\u00a0<\/b><\/span><\/span>e sentido de\u00a0<\/b><\/span><\/span>B para A no fio 2.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(C) Campo magn\u00e9tico entrando na folha (X<\/b><\/span><\/span>) e\u00a0<\/b><\/span><\/span>sentido da corrente el\u00e9trica de B para A no fio 1\u00a0<\/b><\/span><\/span>e sentido de\u00a0<\/b><\/span><\/span>B para A no fio 2.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(D) Campo magn\u00e9tico saindo na folha (\u2022)<\/b><\/span><\/span>\u00a0e\u00a0<\/b><\/span><\/span>sentido da corrente el\u00e9trica de B para A nos fios 1 e 2.<\/b><\/span><\/span><\/span><\/span><\/p>\n

11-(FUVEST-SP-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

As\u00a0<\/b><\/span><\/span>figuras representam arranjos de fios longos, retil\u00edneos, paralelos<\/b><\/span><\/span>\u00a0e <\/b><\/span><\/span>percorridos\u00a0<\/b><\/span><\/span>por\u00a0<\/b><\/span><\/span>correntes el\u00e9tricas de mesma intensidade.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Os fios est\u00e3o orientados perpendicularmente ao plano desta p\u00e1gina<\/b><\/span><\/span>\u00a0e dispostos segundo os\u00a0<\/b><\/span><\/span>v\u00e9rtices de um quadrado.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span>campo magn\u00e9tico total \u00e9 nulo no centro do quadrado apenas<\/b><\/span><\/span>\u00a0em<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Campo magn\u00e9tico gerado por uma espira circular e por um solenoide<\/span><\/span><\/span><\/p>\n

12-(EsPCEx- AMAN \u2013 SP- RJ \u2013 2016\/17)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Dois fios\u00a0<\/b><\/span><\/span>condutores<\/b><\/span><\/span>\u00a0retil\u00edneos,<\/b><\/span><\/span>\u00a0<\/b><\/span>muito longos e paralelos entre si,\u00a0<\/b><\/span><\/span>s\u00e3o <\/b><\/span><\/span>percorridos por correntes el\u00e9tricas d<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>intensidade\u00a0<\/b><\/span><\/span>distintas,\u00a0<\/b><\/span><\/span>i1\u00a0e i2, de sentidos opostos.<\/b><\/span><\/span><\/span><\/span>\"\"<\/p>\n

Uma\u00a0<\/b><\/span><\/span>espira circular condutora de raio R\u00a0<\/b><\/span><\/span>\u00e9 <\/b><\/span><\/span>colocada\u00a0<\/b><\/span><\/span>entre os dois fios e\u00a0<\/b><\/span><\/span>\u00e9 percorrida por uma corrente el\u00e9trica i.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>espira e os fios est\u00e3o no mesmo plano.<\/b><\/span><\/span><\/span><\/span><\/p>\n

O\u00a0<\/b><\/span><\/span>centro da espira dista de 3 R\u00a0<\/b><\/span><\/span>de cada fio, conforme o\u00a0<\/b><\/span><\/span>desenho.\u00a0<\/b><\/span><\/span>Para que o\u00a0<\/b><\/span><\/span>vetor campo magn\u00e9tico resultante, no centro da espira, seja nulo,\u00a0<\/b><\/span><\/span>a i<\/b><\/span><\/span>ntensidade<\/b><\/span><\/span>\u00a0da\u00a0<\/b><\/span><\/span>corrente el\u00e9trica i\u00a0<\/b><\/span><\/span>e seu <\/b><\/span><\/span>sentido,<\/b><\/span><\/span>\u00a0tomando como\u00a0<\/b><\/span><\/span>refer\u00eancia o desenho, <\/b><\/span><\/span>s\u00e3o respectivamente:<\/b><\/span><\/span><\/span><\/span><\/p>\n

a)\u00a0<\/b><\/span><\/span>(i1\u00a0+ i2)\/3 e hor\u00e1rio<\/b><\/span><\/span><\/span><\/span><\/p>\n

b)\u00a0<\/b><\/span><\/span>(i1\u00a0\u2013 i2)\/3\u03c0 e anti-hor\u00e1rio<\/b><\/span><\/span><\/span><\/span><\/p>\n

c)\u00a0<\/b><\/span><\/span>(i1\u00a0\u2013 i2)\/3\u03c0 e hor\u00e1rio<\/b><\/span><\/span><\/span><\/span><\/p>\n

d)\u00a0<\/b><\/span><\/span>(i1\u00a0+ i2)\/3\u03c0 e hor\u00e1rio<\/b><\/span><\/span><\/span><\/span><\/p>\n

e)\u00a0<\/b><\/span><\/span>(i1\u00a0+ i2)\/3\u03c0 e anti-hor\u00e1rio<\/b><\/span><\/span><\/span><\/span><\/p>\n

 <\/p>\n

13-(FGV-SP-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

As\u00a0<\/b><\/span><\/span>figuras representam dois exemplos de solenoides<\/b><\/span><\/span>, dispositivos que\u00a0<\/b><\/span><\/span>consistem<\/b><\/span><\/span>\u00a0em\u00a0<\/b><\/span><\/span>um fio condutor enrolado.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Tal enrolamento pode se dar em torno de um n\u00facleo\u00a0<\/b><\/span><\/span>feito de\u00a0<\/b><\/span><\/span>algum material\u00a0<\/b><\/span><\/span>ou, simplesmente,\u00a0<\/b><\/span><\/span>no ar. Cada volta de fio<\/b><\/span><\/span>\u00a0\u00e9 denominada\u00a0<\/b><\/span><\/span>espira.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A\u00a0<\/b><\/span><\/span>passagem de uma corrente el\u00e9trica atrav\u00e9s desse fio cria,\u00a0<\/b><\/span><\/span>no\u00a0<\/b><\/span><\/span>interior do solenoide,\u00a0<\/b><\/span><\/span>um\u00a0<\/b><\/span><\/span>campo magn\u00e9tico\u00a0<\/b><\/span><\/span>cuja intensidade<\/b><\/span><\/span><\/span><\/span><\/p>\n

(A)\u00a0<\/b><\/span><\/span>\u00e9\u00a0<\/b><\/span><\/span>diretamente proporcional ao quadrado da intensidade da corrente el\u00e9trica e ao comprimento do solenoide.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(B)<\/b><\/span><\/span>\u00a0\u00e9\u00a0<\/b><\/span><\/span>diretamente proporcional \u00e0 densidade das espiras,\u00a0<\/b><\/span><\/span>ou seja, ao <\/b><\/span><\/span>n\u00famero de espiras por unidade de comprimento<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(C)\u00a0<\/b><\/span><\/span>\u00e9\u00a0<\/b><\/span><\/span>diretamente proporcional ao n\u00famero total de espiras do solenoide\u00a0<\/b><\/span><\/span>e ao\u00a0<\/b><\/span><\/span>seu comprimento.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(D) independe da dist\u00e2ncia entre as espiras,\u00a0<\/b><\/span><\/span>mas\u00a0<\/b><\/span><\/span>depende do material de que \u00e9 feito o n\u00facleo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(E)\u00a0<\/b><\/span><\/span>\u00e9 a\u00a0<\/b><\/span><\/span>maior poss\u00edvel quando o material componente do n\u00facleo \u00e9 diamagn\u00e9tico ou paramagn\u00e9tico.<\/b><\/span><\/span><\/span><\/span><\/p>\n

14-(Faculdade Israelita de Ci\u00eancias da Sa\u00fade Albert Einstein \u2013 SP \u2013 016)<\/b><\/span><\/span><\/span><\/p>\n

Custo e manuten\u00e7\u00e3o dos aparelhos de imagem encarecem exames<\/b><\/span><\/span><\/p>\n

\u00c9 ineg\u00e1vel que a\u00a0<\/b><\/span><\/span>evolu\u00e7\u00e3o da medicina diagn\u00f3stica\u00a0<\/b><\/span><\/span>permitiu\u00a0<\/b><\/span><\/span>avan\u00e7os<\/b><\/span><\/span>\u00a0sem precedentes na\u00a0<\/b><\/span><\/span>preven\u00e7\u00e3o e tratamento de v\u00e1rios tipos de doen\u00e7as.<\/b><\/span><\/span><\/p>\n

Se por um lado a\u00a0<\/b><\/span><\/span>tecnologia<\/b><\/span><\/span>\u00a0propiciou\u00a0<\/b><\/span><\/span>fidelidade<\/b><\/span><\/span>\u00a0cada vez maior nas <\/b><\/span><\/span>imagens obtidas do interior do corpo humano<\/b><\/span><\/span>, por outro ela tamb\u00e9m cobra o seu pre\u00e7o. Um exame de\u00a0<\/b><\/span><\/span>resson\u00e2ncia magn\u00e9tica<\/b><\/span><\/span>, por exemplo, pode chegar a\u00a0<\/b><\/span><\/span>R$ 1 200,00 em m\u00e9dia<\/b><\/span><\/span>, se for feito sem material para contraste, e\u00a0<\/b><\/span><\/span>R$ 1 800,00 se essa subst\u00e2ncia para contraste for utilizada.<\/b><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>resson\u00e2ncia nuclear magn\u00e9tica<\/b><\/span><\/span>, ou simplesmente\u00a0<\/b><\/span><\/span>resson\u00e2ncia magn\u00e9tica<\/b><\/span><\/span>, \u00e9 um m\u00e9todo de<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

diagn\u00f3stico por imagem que usa\u00a0<\/b><\/span><\/span>ondas de radiofrequ\u00eancia e um forte campo magn\u00e9tico\u00a0<\/b><\/span><\/span>para obter\u00a0<\/b><\/span><\/span>informa\u00e7\u00f5es detalhadas dos \u00f3rg\u00e3os e tecidos internos do corpo<\/b><\/span><\/span>, sem a utiliza\u00e7\u00e3o de radia\u00e7\u00e3o<\/b><\/span><\/span><\/p>\n

ionizante.<\/b><\/span><\/span><\/p>\n

Esta t\u00e9cnica provou ser muito\u00a0<\/b><\/span><\/span>valiosa\u00a0<\/b><\/span><\/span>para o\u00a0<\/b><\/span><\/span>diagn\u00f3stic<\/b><\/span><\/span>o de uma ampla gama de condi\u00e7\u00f5es cl\u00ednicas em\u00a0<\/b><\/span><\/span>todas as partes do corpo.<\/b><\/span><\/span><\/p>\n

O\u00a0<\/b><\/span><\/span>aparelho<\/b><\/span><\/span>\u00a0em que o exame \u00e9 feito\u00a0<\/b><\/span><\/span>consta de um tubo circundado por um grande eletro\u00edm\u00e3, no<\/b><\/span><\/span><\/p>\n

interior do qual \u00e9 produzido um potente campo magn\u00e9tico.<\/b><\/span><\/span><\/p>\n

Na t\u00e9cnica\u00a0<\/b><\/span><\/span>de resson\u00e2ncia magn\u00e9tica aplicada \u00e0 medicina\u00a0<\/b><\/span><\/span>trabalha-se principalmente com as\u00a0<\/b><\/span><\/span>propriedades magn\u00e9ticas do n\u00facleo de hidrog\u00eanio<\/b><\/span><\/span>, que \u00e9 o menor n\u00facleo que existe e consta de\u00a0<\/b><\/span><\/span>apenas um pr\u00f3ton.<\/b><\/span><\/span><\/p>\n

O\u00a0<\/b><\/span><\/span>paciente<\/b><\/span><\/span>\u00a0a ser examinado \u00e9\u00a0<\/b><\/span><\/span>colocado dentro de um campo magn\u00e9tico intenso<\/b><\/span><\/span>, o qual pode\u00a0<\/b><\/span><\/span>variar de 0,2 a 3,0 teslas,\u00a0<\/b><\/span><\/span>dependendo do aparelho. Esse\u00a0<\/b><\/span><\/span>campo magn\u00e9tico externo\u00a0<\/b><\/span><\/span>\u00e9 gerado pela\u00a0<\/b><\/span><\/span>elevada intensidade de corrente el\u00e9trica circulando por uma bobina supercondutora que precisa ser continuamente refrigerada a uma temperatura de 4K (Kelvin),por meio de h\u00e9lio l\u00edquido, a fim de manter as caracter\u00edsticas supercondutoras do magneto.<\/b><\/span><\/span><\/p>\n

(Dispon\u00edvel em: http:\/\/www.famerp.br\/projis\/grp25\/ressonancia.html. Adaptado.)<\/b><\/span><\/span><\/p>\n

Nas\u00a0<\/b><\/span><\/span>proximidades da superf\u00edcie da Terra<\/b><\/span><\/span>, a\u00a0<\/b><\/span><\/span>intensidade m\u00e9dia do campo magn\u00e9tico \u00e9 de\u00a0<\/b><\/span><\/span>5.10<\/b><\/span><\/span>-5<\/b><\/span><\/sup><\/span> T<\/b><\/span><\/span><\/p>\n

e, conforme o\u00a0<\/b><\/span><\/span>texto informa<\/b><\/span><\/span>,\u00a0<\/b><\/span><\/span>a intensidade do campo magn\u00e9tico produzido por alguns aparelhos de resson\u00e2ncia magn\u00e9tica pode chegar a <\/b><\/span><\/span>3T<\/b><\/span><\/span>.<\/b><\/span><\/span><\/p>\n

Considere, por hip\u00f3tese, esses\u00a0<\/b><\/span><\/span>campos magn\u00e9ticos uniformes\u00a0<\/b><\/span><\/span>e produzidos por\u00a0<\/b><\/span><\/span>duas bobinas chatas distintas,<\/b><\/span><\/span>\u00a0de\u00a0<\/b><\/span><\/span>raios iguais a 1m para o aparelho e R<\/b><\/span><\/span>T<\/b><\/span><\/sub><\/span>\u00a0(raio da Terra) para a bobina da Terra<\/b><\/span><\/span>;<\/b><\/span><\/span><\/p>\n

cada uma delas\u00a0<\/b><\/span><\/span>composta por espiras justapostas<\/b><\/span><\/span>; percorridas\u00a0<\/b><\/span><\/span>pela mesma intensidade de corrente el\u00e9trica e mesma permeabilidade magn\u00e9tica do meio.<\/b><\/span><\/span><\/p>\n

Determine<\/b><\/span><\/span>\u00a0a raz\u00e3o <\/b><\/span><\/span>(N<\/b><\/span><\/span>Terra<\/b><\/span><\/sub><\/span> \/N<\/b><\/span><\/span>aparelho<\/b><\/span><\/sub><\/span>) entre\u00a0<\/b><\/span><\/span>o n\u00famero de espiras das bobinas chatas da Terra e do\u00a0aparelho, respectivamente.<\/b><\/span><\/span>\u00a0Para simplificar os c\u00e1lculos,\u00a0<\/b><\/span><\/span>adote o raio da Terra igual a 6 000 km.<\/b><\/span><\/span><\/p>\n

15-(PUC-SP-016)<\/b><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>figura\u00a0<\/b><\/span><\/span>representa\u00a0<\/b><\/span><\/span>dois fios condutores retil\u00edneos\u00a0<\/b><\/span><\/span>e muito compridos, <\/b><\/span><\/span>paralelos e percorridos por correntes el\u00e9tricas de mesma intensidade ( iF),\u00a0<\/b><\/span><\/span>por\u00e9m, de\u00a0<\/b><\/span><\/span>sentidos contr\u00e1rios.<\/b><\/span><\/span>\"\"<\/p>\n

Entre os fios\u00a0<\/b><\/span><\/span>h\u00e1 uma\u00a0<\/b><\/span><\/span>espira circular de raio R percorrida<\/b><\/span><\/span>\u00a0por uma\u00a0<\/b><\/span><\/span>corrente el\u00e9trica de intensidade ( iE\u00a0).<\/b><\/span><\/span><\/p>\n

Determine a\u00a0<\/b><\/span><\/span>raz\u00e3o iF\/iE\u00a0<\/b><\/span><\/span>e o\u00a0<\/b><\/span><\/span>sentido da corrente el\u00e9trica na espira circular\u00a0<\/b><\/span><\/span>para que o\u00a0<\/b><\/span><\/span>campo de indu\u00e7\u00e3o magn\u00e9tica resultante no centro da espira seja nulo.<\/b><\/span><\/span><\/p>\n

Os\u00a0<\/b><\/span><\/span>fios condutores e a espira circular\u00a0<\/b><\/span><\/span>est\u00e3o situados no\u00a0<\/b><\/span><\/span>mesmo <\/b><\/span><\/span><\/p>\n

plano<\/b><\/span><\/span><\/p>\n

(A)\u00a0<\/b><\/span><\/span>\uf070<\/b><\/span><\/span><\/span>\u00a0e o sentido da corrente na espira deve ser anti-hor\u00e1rio.<\/b><\/span><\/span><\/p>\n

(B)\u00a0<\/b><\/span><\/span>\uf070<\/b><\/span><\/span><\/span>\u00a0e o sentido da corrente na espira deve ser hor\u00e1rio.<\/b><\/span><\/span><\/p>\n

(C)\u00a0<\/b><\/span><\/span>1,5<\/b><\/span><\/span>\uf070<\/b><\/span><\/span><\/span>\u00a0e o sentido da corrente na espira deve ser hor\u00e1rio.<\/b><\/span><\/span><\/p>\n

(D)\u00a0<\/b><\/span><\/span>1,5<\/b><\/span><\/span>\uf070<\/b><\/span><\/span><\/span>\u00a0e o sentido da corrente na espira deve ser anti-hor\u00e1rio.<\/b><\/span><\/span><\/p>\n

Fluxo magn\u00e9tico- Indu\u00e7\u00e3o eletromagn\u00e9tica \u2013 Sentido da corrente el\u00e9trica induzida<\/span><\/span><\/span><\/p>\n

16-(FAMERP-SP-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Uma\u00a0<\/b><\/span><\/span>espira met\u00e1lica retangular ABCD,<\/b><\/span><\/span>\u00a0de\u00a0<\/b><\/span><\/span>\u00e1rea constante<\/b><\/span><\/span>, est\u00e1<\/b><\/span><\/span>totalmente imersa\u00a0<\/b><\/span><\/span>em um\u00a0<\/b><\/span><\/span>campo magn\u00e9tico uniforme horizontal\u00a0<\/b><\/span><\/span>criado na regi\u00e3o entre\u00a0<\/b><\/span><\/span>dois polos magn\u00e9ticos norte e sul,\u00a0<\/b><\/span><\/span>como representado\u00a0<\/b><\/span><\/span>na figura.<\/b><\/span><\/span><\/span><\/span>\"\"<\/p>\n

Inicialment<\/b><\/span><\/span>e, a\u00a0<\/b><\/span><\/span>espira est\u00e1 em repous<\/b><\/span><\/span>o em um\u00a0<\/b><\/span><\/span>plano vertical perpendicular \u00e0s linhas de indu\u00e7\u00e3o do campo magn\u00e9tico.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Suponha que a\u00a0<\/b><\/span><\/span>espira gire 90\u00ba no sentido anti-hor\u00e1rio,\u00a0<\/b><\/span><\/span>em\u00a0<\/b><\/span><\/span>torno<\/b><\/span><\/span>\u00a0de um <\/b><\/span><\/span>eixo vertical, nesse campo magn\u00e9tico. Enquanto isso acontece,<\/b><\/span><\/span><\/span><\/span><\/p>\n

(A) circular\u00e1\u00a0<\/b><\/span><\/span>por ela uma corrente el\u00e9trica induzida\u00a0<\/b><\/span><\/span>sempre no sentido DCBA<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(B) circular\u00e1\u00a0<\/b><\/span><\/span>por ela uma corrente el\u00e9trica induzida,\u00a0<\/b><\/span><\/span>primeiro no sentido DCBA e depois no sentido ABCD. (C) circular\u00e1\u00a0<\/b><\/span><\/span>por ela uma corrente el\u00e9trica induzida\u00a0<\/b><\/span><\/span>sempre no sentido ABCD.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(D) circular\u00e1\u00a0<\/b><\/span><\/span>por ela uma corrente el\u00e9trica induzida,\u00a0<\/b><\/span><\/span>primeiro no sentido ABCD e depois no sentido DCBA. <\/b><\/span><\/span><\/span><\/span><\/p>\n

(E) n\u00e3o circular\u00e1\u00a0<\/b><\/span><\/span>por ela\u00a0<\/b><\/span><\/span>corrente el\u00e9trica induzida.<\/b><\/span><\/span><\/span><\/span><\/p>\n

17-(AFA-SP-015)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Desejando-se determinar a\u00a0<\/b><\/span><\/span>intensidade do campo magn\u00e9tico no interior de um solenoide longo<\/b><\/span><\/span>\u00a0percorrido por uma\u00a0<\/b><\/span><\/span>corrente el\u00e9trica constante<\/b><\/span><\/span>, um professor de f\u00edsica construiu um aparato experimental que consistia, <\/b><\/span><\/span>al\u00e9m do solenoide, de uma balan\u00e7a de bra\u00e7os isolantes e iguais a\u00a0<\/b><\/span><\/span>d1<\/b><\/span><\/span><\/p>\n

e\u00a0<\/b><\/span><\/span>d2<\/b><\/span><\/span>, sendo que o\u00a0<\/b><\/span><\/span>prato em uma das extremidades foi substitu\u00eddo por uma <\/b><\/span><\/span>espira quadrada de lado L,<\/b><\/span><\/span>\u00a0conforme indicado na figura abaixo.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

Quando\u00a0<\/b><\/span><\/span>n\u00e3o circula<\/b><\/span><\/span>\u00a0corrente na espira, a balan\u00e7a se encontra\u00a0<\/b><\/span><\/span>em equil\u00edbrio<\/b><\/span><\/span>\u00a0e o\u00a0<\/b><\/span><\/span>plano da espira est\u00e1<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>na horizontal.<\/b><\/span><\/span>\u00a0Ao fazer passar pela espira uma\u00a0<\/b><\/span><\/span>corrente el\u00e9trica constante i,<\/b><\/span><\/span>\u00a0o\u00a0<\/b><\/span><\/span>equil\u00edbrio da balan\u00e7a \u00e9 restabelecido ao colocar no prato uma\u00a0<\/b><\/span><\/span>massa m<\/b><\/span><\/span>\u00a0. Sendo\u00a0<\/b><\/span><\/span>g o m\u00f3dulo do campo gravitacional local<\/b><\/span><\/span>, o\u00a0<\/b><\/span><\/span>campo magn\u00e9tico no interior do solenoide \u00e9 dado pela express\u00e3o<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

 <\/p>\n

18-(FAMERP-SP-015)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A figura mostra um solenoide colocado sobre uma superf\u00edcie horizontal, ligado a uma bateria, e visto de cima para baixo.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O campo magn\u00e9tico gerado por esse solenoide ser\u00e1 semelhante ao de um \u00edm\u00e3 em forma de barra, tamb\u00e9m sobre uma superf\u00edcie horizontal e visto de cima para baixo, corretamente representado por<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

For\u00e7a eletromotriz induzida
\nTransformadores<\/span><\/span><\/span><\/p>\n

19-(UDESC-SC-016)<\/b><\/span><\/span><\/span><\/p>\n

Com rela\u00e7\u00e3o aos\u00a0<\/b><\/span><\/span>fen\u00f4menos eletromagn\u00e9ticos, analise as proposi\u00e7\u00f5es.<\/b><\/span><\/span><\/p>\n

I.<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>Corrente el\u00e9trica induzida, em um circuito fechado, por um campo magn\u00e9tico vari\u00e1vel no tempo sempre gera um campo magn\u00e9tico que se op\u00f5e \u00e0 mudan\u00e7a desse campo.<\/b><\/span><\/span><\/p>\n

II.<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>Correntes el\u00e9tricas, em circuitos fechados<\/b><\/span><\/span>, podem\u00a0<\/b><\/span><\/span>formar dipolos magn\u00e9ticos<\/b><\/span><\/span>, mas nunca\u00a0<\/b><\/span><\/span>monopolos magn\u00e9ticos.<\/b><\/span><\/span><\/p>\n

III.<\/b><\/span><\/span>\u00a0Ao\u00a0<\/b><\/span><\/span>dividir-se um \u00edm\u00e3 ao meio<\/b><\/span><\/span>, formam-se dois\u00a0<\/b><\/span><\/span>monopolos magn\u00e9ticos, um polo sul e outro polo norte.<\/b><\/span><\/span><\/p>\n

IV.<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>For\u00e7a magn\u00e9tica<\/b><\/span><\/span>\u00a0atua em\u00a0<\/b><\/span><\/span>cargas el\u00e9tricas em repouso e em movimento.<\/b><\/span><\/span><\/p>\n

Assinale a alternativa\u00a0correta:<\/b><\/span><\/span><\/p>\n

A.<\/b><\/span><\/span>\u00a0( ) Somente as afirmativas II e III s\u00e3o verdadeiras.<\/b><\/span><\/span><\/p>\n

B.<\/b><\/span><\/span>\u00a0( ) Somente as afirmativas I, III e IV s\u00e3o verdadeiras.<\/b><\/span><\/span><\/p>\n

C.<\/b><\/span><\/span>\u00a0( ) Somente as afirmativas II e IV s\u00e3o verdadeiras.<\/b><\/span><\/span><\/p>\n

D.<\/b><\/span><\/span>\u00a0( ) Somente as afirmativas I e II s\u00e3o verdadeiras.<\/b><\/span><\/span><\/p>\n

E.<\/b><\/span><\/span>\u00a0( ) Somente as afirmativas I e IV s\u00e3o verdadeiras.<\/b><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

20-(UFRGS-RS-015)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um\u00a0<\/b><\/span><\/span>campo magn\u00e9tico uniforme\u00a0B<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>atravessa\u00a0<\/b><\/span><\/span>perpendicularmente o plano do circuito<\/b><\/span><\/span>\u00a0representado abaixo,\u00a0<\/b><\/span><\/span>direcionado para fora desta p\u00e1gina.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span>fluxo\u00a0<\/b><\/span><\/span>desse campo atrav\u00e9s do circuito\u00a0<\/b><\/span><\/span>aumenta \u00e0 taxa de 1 Wb\/s.<\/b><\/span><\/span><\/p>\n

Nessa situa\u00e7\u00e3o, a leitura do amper\u00edmetro A apresenta, em amp\u00e8res,<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

21-(ENEM-MEC-2014)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span>funcionamento dos geradores de usinas el\u00e9tricas<\/b><\/span><\/span>\u00a0baseia-se no <\/b><\/span><\/span>fen\u00f4meno da indu\u00e7\u00e3o eletromagn\u00e9tica<\/b><\/span><\/span>, descoberto por Michael Faraday no s\u00e9culo XIX. Pode-se <\/b><\/span><\/span>observar esse fen\u00f4meno ao se\u00a0<\/b><\/span><\/span>movimentar um \u00edm\u00e3 e uma espira<\/b><\/span><\/span>\u00a0em sentidos opostos com m\u00f3dulo da velocidade igual a V<\/b><\/span><\/span>, <\/b><\/span><\/span>induzindo uma corrente el\u00e9trica de intensidade i<\/b><\/span><\/span>, como ilustrado na figura.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

A\u00a0<\/b><\/span><\/span>fim de se obter uma corrente com o mesmo sentido da apresentada na figura<\/b><\/span><\/span>,\u00a0<\/b><\/span><\/span>utilizando os<\/b><\/span><\/span><\/p>\n

mesmos materiais<\/b><\/span><\/span>,\u00a0<\/b><\/span><\/span>outra possibilidade \u00e9 mover a espira para a<\/b><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span>a esquerda e o \u00edm\u00e3 para a direita com polaridade invertida.<\/b><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>direita e o \u00edm\u00e3 para a esquerda com a polaridade invertida.<\/b><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span>esquerda e o \u00edm\u00e3 para a esquerda com a mesma polaridade.<\/b><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span>direita e manter o \u00edm\u00e3 em repouso com polaridade invertida.<\/b><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span>esquerda e manter o \u00edm\u00e3 em repouso com a mesma polaridade.<\/b><\/span><\/span><\/p>\n

Como foi obtido o sentido da corrente el\u00e9trica da figura:<\/b><\/span><\/span><\/p>\n

22-(FMABC-SP-015)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um\u00a0<\/b><\/span><\/span>circuito\u00a0<\/b><\/span><\/span>constitu\u00eddo de\u00a0<\/b><\/span><\/span>uma espira quadrada, fixa e de lados iguais a 8 cm,<\/b><\/span><\/span>\u00a0\u00e9 atravessada por\u00a0<\/b><\/span><\/span>linhas de indu\u00e7\u00e3o magn\u00e9tica<\/b><\/span><\/span>, conforme indicado na figura.<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span>vetor campo magn\u00e9tico\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/i><\/span><\/span>tem\u00a0<\/b><\/span><\/span>dire\u00e7\u00e3o constante<\/b><\/span><\/span>\u00a0e,\u00a0<\/b><\/span><\/span>inicialmente, <\/b><\/span><\/span>apresenta uma\u00a0<\/b><\/span><\/span>intensidade de<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>0,6 T.<\/b><\/span><\/span><\/p>\n

Durante um\u00a0<\/b><\/span><\/span>intervalo de tempo de 2 s,<\/b><\/span><\/span>\u00a0a\u00a0<\/b><\/span><\/span>intensidade do campo magn\u00e9tico \u00e9 diminu\u00edda para 0,2 T.<\/b><\/span><\/span>\u00a0Assim, podemos afirmar que a\u00a0<\/b><\/span><\/span>for\u00e7a eletromotriz induzida m\u00e9dia, <\/b><\/span><\/span>nesse intervalo de tempo, corresponde, em\u00a0<\/b><\/span><\/span>milivolt (mV), <\/b><\/span><\/span>aproximadamente, a:<\/b><\/span><\/span><\/p>\n

Dados:\u00a0<\/b><\/span><\/span>cos<\/b><\/span><\/span>\u03b8\u00a0<\/b><\/i><\/span><\/span>= 0,8 e sen<\/b><\/span><\/span>\u03b8\u00a0<\/b><\/i><\/span><\/span>= 0,6<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

23-(UEM-PR-015)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Assinale o que for\u00a0<\/b><\/span><\/span>correto.<\/b><\/span><\/span><\/p>\n

01)<\/b><\/span><\/span>\u00a0Condutores el\u00e9tricos paralelos percorridos por correntes el\u00e9tricas que fluem no mesmo sentido<\/b><\/span><\/span><\/p>\n

repelem-se.<\/b><\/span><\/span><\/p>\n

02)<\/b><\/span><\/span>\u00a0A for\u00e7a eletromotriz induzida em uma espira condutora \u00e9 diretamente proporcional \u00e0 varia\u00e7\u00e3o<\/b><\/span><\/span><\/p>\n

temporal do fluxo magn\u00e9tico que atravessa essa espira.<\/b><\/span><\/span><\/p>\n

04)<\/b><\/span><\/span>\u00a0A for\u00e7a eletromotriz induzida em uma espira condutora \u00e9 inversamente proporcional ao intervalo<\/b><\/span><\/span><\/p>\n

de tempo em que ocorre a varia\u00e7\u00e3o do fluxo magn\u00e9tico que atravessa a espira.<\/b><\/span><\/span><\/p>\n

08)<\/b><\/span><\/span>\u00a0A corrente el\u00e9trica induzida em um circuito el\u00e9trico produz um campo magn\u00e9tico que permite o aumento do fluxo magn\u00e9tico que a induz.<\/b><\/span><\/span><\/p>\n

16)<\/b><\/span><\/span>\u00a0A varia\u00e7\u00e3o temporal do campo magn\u00e9tico em uma determinada regi\u00e3o do espa\u00e7o provoca o<\/b><\/span><\/span><\/p>\n

aparecimento de um campo el\u00e9trico vari\u00e1vel nessa mesma regi\u00e3o.<\/b><\/span><\/span><\/p>\n

 <\/p>\n

 <\/p>\n

Confira a resolu\u00e7\u00e3o comentada dos exerc\u00edcios<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Vestibulares Recentes \u2013 Eletricidade Eletromagnetismo \u2013 2017 \u2013 2016 – 2015 Im\u00e3s e campo magn\u00e9tico 01-(COL\u00c9GIO NAVAL-015) Com rela\u00e7\u00e3o aos\u00a0conceitos de eletricidade e magnetismo, coloque\u00a0V (verdadeiro) ou F (falso)\u00a0nas afirmativas abaixo e, em seguida,\u00a0assinale a op\u00e7\u00e3o\u00a0que representa a\u00a0sequ\u00eancia correta. ( ) Na\u00a0eletriza\u00e7\u00e3o por atrito, o corpo\u00a0perde el\u00e9trons\u00a0passa a\u00a0ter mais pr\u00f3tons do que possu\u00eda anteriormente\u00a0e, nesse caso,\u00a0fica eletrizado com carga positiva.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3299,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-3328","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3328","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/comments?post=3328"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3328\/revisions"}],"predecessor-version":[{"id":3334,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3328\/revisions\/3334"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3299"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=3328"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}