{"id":2892,"date":"2017-04-12T05:30:36","date_gmt":"2017-04-12T05:30:36","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2892"},"modified":"2024-09-02T14:57:53","modified_gmt":"2024-09-02T14:57:53","slug":"eletrodinamica","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/raciocinio-logico\/eletrodinamica\/","title":{"rendered":"Eletrodin\u00e2mica"},"content":{"rendered":"

Racioc\u00ednio L\u00f3gico<\/b><\/span><\/span><\/span><\/p>\n

ELETRODIN\u00c2MICA<\/b><\/span><\/span><\/span><\/p>\n

Como esse conte\u00fado envolve muita teoria, em caso de d\u00favidas voc\u00ea pode <\/b><\/span><\/span><\/span>encontr\u00e1-la em<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>fisicaevestibular.com.br \u2013 Eletrodin\u00e2mica<\/b><\/span><\/span><\/span><\/p>\n

<\/a><\/p>\n

01-(UNIFESP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Para <\/b><\/span><\/span><\/span>compor sua decora\u00e7\u00e3o de Natal,<\/b><\/span><\/span><\/span> um <\/b><\/span><\/span><\/span>comerciante decide construir uma estrela <\/b><\/span><\/span><\/span>para pendurar na <\/b><\/span><\/span><\/span>fachada de sua loja. <\/b><\/span><\/span><\/span><\/p>\n

Para isso, <\/b><\/span><\/span><\/span>utilizar\u00e1 um material <\/b><\/span><\/span><\/span>que, quando\u00a0<\/b><\/span><\/span><\/span>percorrido por corrente el\u00e9trica, brilhe emitindo luz colorida<\/b><\/span><\/span><\/span>.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Ele tem <\/b><\/span><\/span><\/span>\u00e0 sua disposi\u00e7\u00e3o\u00a0barras de diferentes cores desse material,\u00a0cada uma\u00a0<\/b><\/span><\/span><\/span>com\u00a0<\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica constante\u00a0R = 20 \u03a9.<\/b><\/span><\/span><\/span><\/p>\n

Utilizando\u00a0<\/b><\/span><\/span><\/span>dez\u00a0dessas barras, <\/b><\/span><\/span><\/span>ele montou uma <\/b><\/span><\/span><\/span>estrela e conectou os pontos A e B a um\u00a0gerador ideal\u00a0de\u00a0for\u00e7a eletromotriz constante e igual a\u00a0120 V.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Considerando <\/b><\/span><\/span><\/span>desprez\u00edveis as resist\u00eancias el\u00e9tricas dos fios utilizados e das conex\u00f5es feitas, <\/b><\/span><\/span><\/span>calcule:<\/b><\/span><\/span><\/span><\/p>\n

a)\u00a0<\/b><\/span><\/span><\/span>a\u00a0<\/b><\/span><\/span><\/span>resist\u00eancia equivalente, em ohms, da estrela.<\/b><\/span><\/span><\/span><\/p>\n

b)\u00a0<\/b><\/span><\/span><\/span>a\u00a0<\/b><\/span><\/span><\/span>pot\u00eancia el\u00e9trica, em watts, <\/b><\/span><\/span><\/span>dissipada em <\/b><\/span><\/span><\/span>conjunto pelas pontas de cores\u00a0laranja (CAD), azul (DEF) e vermelha (FBG)\u00a0da estrela, quando ela se encontrar acesa.<\/b><\/span><\/span><\/span><\/p>\n

02-(UNESP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>circuito\u00a0representado na figura <\/b><\/span><\/span><\/span>\u00e9 utilizado\u00a0para obter\u00a0<\/b><\/span><\/span><\/span>diferentes intensidades luminosas com a mesma l\u00e2mpada L.<\/b><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span><\/span>chave Ch pode ser ligada ao ponto A ou ao ponto B do circuito. <\/b><\/span><\/span><\/span><\/p>\n

Quando\u00a0<\/b><\/span><\/span><\/span>ligada em B, a\u00a0l\u00e2mpada L dissipa uma\u00a0pot\u00eancia de 60 W\u00a0<\/b><\/span><\/span><\/span>e o\u00a0<\/b><\/span><\/span><\/span>amper\u00edmetro ideal\u00a0\"\"\u00a0indica uma\u00a0corrente el\u00e9trica de intensidade 2 A.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Considerando que o\u00a0<\/b><\/span><\/span><\/span>gerador\u00a0tenha\u00a0for\u00e7a eletromotriz constante E = 100 V\u00a0e\u00a0resist\u00eancia interna desprez\u00edvel, <\/b><\/span><\/span><\/span>que os <\/b><\/span><\/span><\/span>resistores e a l\u00e2mpada tenham resist\u00eancias constantes <\/b><\/span><\/span><\/span>e que <\/b><\/span><\/span><\/span>os fios de liga\u00e7\u00e3o <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>as conex\u00f5es sejam ideais,<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>calcule<\/b><\/span><\/span><\/span> o valor da <\/b><\/span><\/span><\/span>resist\u00eancia\u00a0R<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/sub><\/span>\u00a0da l\u00e2mpada, em ohms<\/b><\/span><\/span><\/span>, e a\u00a0<\/b><\/span><\/span><\/span>energia\u00a0dissipada pelo circuito, em joules, se ele permanecer\u00a0ligado durante dois minutos com a chave na posi\u00e7\u00e3o A.<\/b><\/span><\/span><\/span><\/p>\n

03-(ACAFE-SC)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Em uma <\/b><\/span><\/span><\/span>situa\u00e7\u00e3o cotidiana, <\/b><\/span><\/span><\/span>uma pessoa\u00a0<\/b><\/span><\/span><\/span>liga duas l\u00e2mpadas incandescentes em paralelo <\/b><\/span><\/span><\/span>em uma <\/b><\/span><\/span><\/span>rede de 220V. <\/b><\/span><\/span><\/span><\/p>\n

As <\/b><\/span><\/span><\/span>l\u00e2mpadas apresentam\u00a0certa intensidade luminosa (brilho),<\/b><\/span><\/span><\/span> sendo que a\u00a0<\/b><\/span><\/span><\/span>l\u00e2mpada 2 <\/b><\/span><\/span><\/span>tem um <\/b><\/span><\/span><\/span>filamento de mesmo material, mesmo comprimento, mas \u00e9 mais grosso que o filamento da l\u00e2mpada 1.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Nessas condi\u00e7\u00f5es, a\u00a0<\/b><\/span><\/span><\/span>alternativa\u00a0correta\u00a0\u00e9:<\/b><\/span><\/span><\/span><\/p>\n

A)\u00a0Desligando <\/b><\/span><\/span><\/span>a l\u00e2mpada <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>,<\/b><\/span><\/span><\/span> a l\u00e2mpada <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0diminui o seu brilho.<\/b><\/span><\/span><\/span><\/p>\n

B)\u00a0<\/b><\/span><\/span><\/span>A l\u00e2mpada<\/b><\/span><\/span><\/span> L<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0brilha mais que a <\/b><\/span><\/span><\/span>l\u00e2mpada <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

C)\u00a0<\/b><\/span><\/span><\/span>As l\u00e2mpadas <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0tem o mesmo brilho.<\/b><\/span><\/span><\/span><\/p>\n

D)\u00a0<\/b><\/span><\/span><\/span>A l\u00e2mpada <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0brilha mais que a <\/b><\/span><\/span><\/span>l\u00e2mpada <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

04-(UNESP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Para <\/b><\/span><\/span><\/span>compor a\u00a0decora\u00e7\u00e3o de um ambiente,\u00a0duas l\u00e2mpadas id\u00eanticas, L<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>com\u00a0<\/b><\/span><\/span><\/span>valores nominais\u00a0(100 V \u2013 100 W),\u00a0<\/b><\/span><\/span><\/span>devem <\/b><\/span><\/span><\/span>ser ligadas em\u00a0paralelo a uma fonte de tens\u00e3o constante de\u00a0200 V. <\/b><\/span><\/span><\/span>Deseja-se que\u00a0<\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0brilhe\u00a0com uma\u00a0pot\u00eancia de 100 W\u00a0<\/b><\/span><\/span><\/span>e que <\/b><\/span><\/span><\/span>L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0brilhe\u00a0com uma\u00a0pot\u00eancia de 64 W.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Para que as <\/b><\/span><\/span><\/span>l\u00e2mpadas n\u00e3o queimem,\u00a0dois resistores \u00f4hmicos, R<\/b><\/span><\/span><\/span>1\u00a0<\/b><\/span><\/span><\/sub><\/span>e R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>com <\/b><\/span><\/span><\/span>valores convenientes,\u00a0<\/b><\/span><\/span><\/span>s\u00e3o\u00a0<\/b><\/span><\/span><\/span>ligados em\u00a0s\u00e9rie <\/b><\/span><\/span><\/span>com<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sub><\/span>as <\/b><\/span><\/span><\/span>respectivas l\u00e2mpadas, <\/b><\/span><\/span><\/span>conforme o <\/b><\/span><\/span><\/span>esquema <\/b><\/span><\/span><\/span>representado<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sub><\/span>na <\/b><\/span><\/span><\/span>figura.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Considerando <\/b><\/span><\/span><\/span>todos os fios utilizados na liga\u00e7\u00e3o como ideais<\/b><\/span><\/span><\/span> e que as\u00a0<\/b><\/span><\/span><\/span>l\u00e2mpadas estejam acesas\u00a0e\u00a0brilhando com as pot\u00eancias desejadas, <\/b><\/span><\/span><\/span>\u00e9 <\/b><\/span><\/span><\/span>correto<\/b><\/span><\/span><\/span> afirmar que os\u00a0<\/b><\/span><\/span><\/span>valores das resist\u00eancias de R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, em ohms,\u00a0s\u00e3o, respectivamente,<\/b><\/span><\/span><\/span> iguais a<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

05-(AFA)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Disp\u00f5e-se <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>duas pilhas id\u00eanticas <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>f.e.m \u03b5 e resist\u00eancia interna r constante<\/b><\/span><\/span><\/span> e de um <\/b><\/span><\/span><\/span>reostato, cuja resist\u00eancia el\u00e9trica R varia de zero at\u00e9 6 r. <\/b><\/span><\/span><\/span>\"\"<\/p>\n

Essas pilhas <\/b><\/span><\/span><\/span>podem ser <\/b><\/span><\/span><\/span>associadas em s\u00e9rie ou em paralelo, <\/b><\/span><\/span><\/span>conforme <\/b><\/span><\/span><\/span>ilustram as figuras I e II, <\/b><\/span><\/span><\/span>respectivamente.<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>gr\u00e1fico <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>melhor representa a pot\u00eancia P dissipada pelo reostato, <\/b><\/span><\/span><\/span>para <\/b><\/span><\/span><\/span>cada uma <\/b><\/span><\/span><\/span>das <\/b><\/span><\/span><\/span>associa\u00e7\u00f5es, <\/b><\/span><\/span><\/span><\/p>\n

em fun\u00e7\u00e3o da resist\u00eancia R \u00e9<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

06-(UFSCAR-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>professor pede a seus alunos <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>tabelem as leituras do\u00a0volt\u00edmetro\u00a0<\/b><\/span><\/span><\/span>e do amper\u00edmetro <\/b><\/span><\/span><\/span>associados aos circuitos 1, 2 e 3, <\/b><\/span><\/span><\/span>quando esses <\/b><\/span><\/span><\/span>circuitos s\u00e3o conectados, um de cada vez, <\/b><\/span><\/span><\/span>aos <\/b><\/span><\/span><\/span>terminais A e B de um\u00a0gerador ideal.<\/b><\/span><\/span><\/span> Os <\/b><\/span><\/span><\/span>resistores <\/b><\/span><\/span><\/span>utilizados t\u00eam\u00a0<\/b><\/span><\/span><\/span>igual\u00a0valor \u00f4hmico.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Ap\u00f3s a s\u00e9rie de leituras, <\/b><\/span><\/span><\/span>os <\/b><\/span><\/span><\/span>alunos constru\u00edram <\/b><\/span><\/span><\/span>a seguinte <\/b><\/span><\/span><\/span>tabela:<\/b><\/span><\/span><\/span>\"\"<\/p>\n

A partir da <\/b><\/span><\/span><\/span>an\u00e1lise da tabela, <\/b><\/span><\/span><\/span>os alunos puderam <\/b><\/span><\/span><\/span>concluir acertadamente que, <\/b><\/span><\/span><\/span>em\u00a0<\/b><\/span><\/span><\/span>circuitos s\u00e9rie, <\/b><\/span><\/span><\/span>\u00e0 <\/b><\/span><\/span><\/span>medida que se\u00a0aumenta o n\u00famero de resistores associados, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>resist\u00eancia equivalente <\/b><\/span><\/span><\/span>da <\/b><\/span><\/span><\/span>associa\u00e7\u00e3o<\/b><\/span><\/span><\/span>\u00a0_________ ,\u00a0a <\/b><\/span><\/span><\/span>diferen\u00e7a de potencial <\/b><\/span><\/span><\/span>entre os <\/b><\/span><\/span><\/span>extremos de um mesmo resistor<\/b><\/span><\/span><\/span><\/p>\n

____________ e a <\/b><\/span><\/span><\/span>intensidade de\u00a0corrente el\u00e9trica no\u00a0circuito<\/b><\/span><\/span><\/span>___________ .<\/b><\/span><\/span><\/span><\/p>\n

Assinale a alternativa <\/b><\/span><\/span><\/span>que <\/b><\/span><\/span><\/span>preenche, correta e respectivamente, as lacunas do texto.<\/b><\/span><\/span><\/span><\/p>\n

(A) <\/b><\/span><\/span><\/span>diminui \u2013 diminui \u2013 diminui<\/b><\/span><\/span><\/span><\/p>\n

(B) <\/b><\/span><\/span><\/span>diminui \u2013 aumenta \u2013 aumenta<\/b><\/span><\/span><\/span><\/p>\n

(C) <\/b><\/span><\/span><\/span>aumenta \u2013 aumenta \u2013 aumenta<\/b><\/span><\/span><\/span><\/p>\n

(D) <\/b><\/span><\/span><\/span>aumenta \u2013 aumenta \u2013 diminui<\/b><\/span><\/span><\/span><\/p>\n

(E) <\/b><\/span><\/span><\/span>aumenta \u2013 diminui \u2013 diminui<\/b><\/span><\/span><\/span><\/p>\n

07-(UERJ-RJ)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Cinco resistores <\/b><\/span><\/span><\/span>de\u00a0<\/b><\/span><\/span><\/span>mesma resist\u00eancia\u00a0R\u00a0<\/b><\/span><\/span><\/span>est\u00e3o <\/b><\/span><\/span><\/span>conectados \u00e0 bateria\u00a0ideal E\u00a0de um autom\u00f3vel,<\/b><\/span><\/span><\/span><\/p>\n

conforme mostra o <\/b><\/span><\/span><\/span>esquema:<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Inicialmente, a <\/b><\/span><\/span><\/span>bateria fornece ao circuito uma pot\u00eancia\u00a0P<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Ao\u00a0<\/b><\/span><\/span><\/span>estabelecer um curto-circuito <\/b><\/span><\/span><\/span>entre os <\/b><\/span><\/span><\/span>pontos M e N,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>pot\u00eancia fornecida \u00e9 igual a P<\/b><\/span><\/span><\/span>f<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>raz\u00e3o \u00e9\u00a0Pf\/Pi\u00a0<\/b><\/span><\/span><\/span>\u00e9 dada por:<\/b><\/span><\/span><\/span><\/p>\n

(A) <\/b><\/span><\/span><\/span><\/span>7\/9 <\/b><\/span><\/span><\/span><\/span><\/p>\n

(B) <\/b><\/span><\/span><\/span><\/span>14\/15 <\/b><\/span><\/span><\/span><\/span><\/p>\n

(C) <\/b><\/span><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/span><\/span><\/p>\n

(D) <\/b><\/span><\/span><\/span><\/span>7\/6<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

A\u00a0<\/b><\/span><\/span><\/span>curva\u00a0caracter\u00edstica\u00a0<\/b><\/span><\/span><\/span>de\u00a0uma\u00a0<\/b><\/span><\/span><\/span>l\u00e2mpada\u00a0do\u00a0tipo\u00a0led\u00a0<\/b><\/span><\/span><\/span>(diodo\u00a0emissor\u00a0de\u00a0luz)\u00a0\u00e9 <\/b><\/span><\/span><\/span>mostrada<\/b><\/span><\/span><\/span> no <\/b><\/span><\/span><\/span>gr\u00e1fico.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Essa\u00a0l\u00e2mpada\u00a0<\/b><\/span><\/span><\/span>e\u00a0um\u00a0<\/b><\/span><\/span><\/span>resistor\u00a0de\u00a0resist\u00eancia\u00a0 R\u00a0 <\/b><\/span><\/span><\/span>est\u00e3o\u00a0 <\/b><\/span><\/span><\/span>ligados\u00a0 em\u00a0 s\u00e9rie\u00a0 <\/b><\/span><\/span><\/span>a\u00a0 uma\u00a0 <\/b><\/span><\/span><\/span>bateria\u00a0 de\u00a0 4,5\u00a0V,\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

como\u00a0<\/b><\/span><\/span><\/span>representado\u00a0na\u00a0figura\u00a0ao\u00a0lado do gr\u00e1fico.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Nessa\u00a0condi\u00e7\u00e3o,\u00a0<\/b><\/span><\/span><\/span>a\u00a0<\/b><\/span><\/span><\/span>tens\u00e3o\u00a0na\u00a0l\u00e2mpada\u00a0\u00e9\u00a02,5\u00a0V.\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Qual\u00a0\u00e9\u00a0o\u00a0<\/b><\/span><\/span><\/span>valor\u00a0da\u00a0corrente\u00a0i<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span>no\u00a0<\/b><\/span><\/span><\/span>resistor?<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Determine\u00a0o\u00a0<\/b><\/span><\/span><\/span>valor\u00a0da\u00a0resist\u00eancia\u00a0R.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>A\u00a0<\/b><\/span><\/span><\/span>bateria\u00a0de\u00a04,5\u00a0V\u00a0\u00e9\u00a0substitu\u00edda\u00a0por\u00a0outra\u00a0de\u00a03\u00a0V,\u00a0<\/b><\/span><\/span><\/span>que\u00a0<\/b><\/span><\/span><\/span>fornece\u00a060\u00a0mW\u00a0de\u00a0pot\u00eancia\u00a0<\/b><\/span><\/span><\/span>ao\u00a0circuito,\u00a0<\/b><\/span><\/span><\/span>sem\u00a0<\/b><\/span><\/span><\/span><\/p>\n

que\u00a0sejam\u00a0trocados\u00a0a\u00a0l\u00e2mpada\u00a0e\u00a0o\u00a0resistor.
\nNessas\u00a0condi\u00e7\u00f5es<\/b><\/span><\/span><\/span>,\u00a0qual\u00a0\u00e9\u00a0a\u00a0<\/b><\/span><\/span><\/span>pot\u00eancia\u00a0P<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span>\u00a0dissipada\u00a0no\u00a0resistor?\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

Dois fios met\u00e1licos, F<\/b><\/span><\/span><\/span>1\u00a0<\/b><\/span><\/span><\/sub><\/span>e F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>cil\u00edndricos, do <\/b><\/span><\/span><\/span>mesmo material de resistividade \u03c1, <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>se\u00e7\u00f5es transversais de \u00e1reas, respectivamente, A<\/b><\/span><\/span><\/span>1\u00a0<\/b><\/span><\/span><\/sub><\/span>e A<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=2A<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>t\u00eam <\/b><\/span><\/span><\/span>comprimento L e s\u00e3o emendados, como ilustra a figura abaixo.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>sistema formado pelos fios \u00e9 conectado <\/b><\/span><\/span><\/span>a uma <\/b><\/span><\/span><\/span>bateria de tens\u00e3o V.<\/b><\/span><\/span><\/span><\/p>\n

Nessas condi\u00e7\u00f5es, a <\/b><\/span><\/span><\/span>diferen\u00e7a de potencial V<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, entre as extremidades de F<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, e V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, entre as de F<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, s\u00e3o tais que<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/4 <\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/2 <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 2V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 4V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span><\/p>\n

10-(UNESP-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Dois resistores \u00f4hmicos, R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>podem ser <\/b><\/span><\/span><\/span>associados em s\u00e9rie ou em paralelo.<\/b><\/span><\/span><\/span> <\/b>\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>resist\u00eancia equivalente quando s\u00e3o associados em s\u00e9rie \u00e9 R<\/b><\/span><\/span><\/span>S\u00a0<\/b><\/span><\/span><\/sub><\/span>e quando <\/b><\/span><\/span><\/span>s\u00e3o associados em paralelo \u00e9 R<\/b><\/span><\/span><\/span>p<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

No <\/b><\/span><\/span><\/span>gr\u00e1fico, a curva S <\/b><\/span><\/span><\/span>representa a <\/b><\/span><\/span><\/span>varia\u00e7\u00e3o da diferen\u00e7a de potencial el\u00e9trico entre os extremos da associa\u00e7\u00e3o dos dois resistores em s\u00e9rie, <\/b><\/span><\/span><\/span>em <\/b><\/span><\/span><\/span>fun\u00e7\u00e3o da intensidade de corrente el\u00e9trica que <\/b><\/span><\/span><\/span>atravessa a <\/b><\/span><\/span><\/span>associa\u00e7\u00e3o de resist\u00eancia equivalente R<\/b><\/span><\/span><\/span>S<\/b><\/span><\/span><\/sub><\/span>\u00a0,<\/b><\/span><\/span><\/span> e a <\/b><\/span><\/span><\/span>curva P representa a varia\u00e7\u00e3o da diferen\u00e7a de potencial el\u00e9trico entre os extremos da associa\u00e7\u00e3o dos dois resistores em paralelo R<\/b><\/span><\/span><\/span>p<\/b><\/span><\/span><\/sub><\/span>, em fun\u00e7\u00e3o da intensidade da corrente el\u00e9trica que atravessa a associa\u00e7\u00e3o de resist\u00eancia equivalente R<\/b><\/span><\/span><\/span>p<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

Considere a <\/b><\/span><\/span><\/span>associa\u00e7\u00e3o seguinte, <\/b><\/span><\/span><\/span>constitu\u00edda por <\/b><\/span><\/span><\/span>dois resistores R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e dois resistores R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

De acordo com as <\/b><\/span><\/span><\/span>informa\u00e7\u00f5es e desprezando a resist\u00eancia el\u00e9trica dos fios de liga\u00e7\u00e3o,\u00a0<\/b><\/span><\/span><\/span>calcule a <\/b><\/span><\/span><\/span>resist\u00eancia equivalente da associa\u00e7\u00e3o representada na figura e os valores de R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0, ambos em ohms.<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

No <\/b><\/span><\/span><\/span>fen\u00f4meno <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>\u201cMagnetoimped\u00e2ncia gigante\u201d, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica de determinado material <\/b><\/span><\/span><\/span>pelo qual <\/b><\/span><\/span><\/span>circula uma corrente alternada de\u00a0frequ\u00eancia\u00a0<\/b><\/span><\/span><\/span>f\u00a0<\/b><\/i><\/span><\/span><\/span>varia com a aplica\u00e7\u00e3o de\u00a0um campo magn\u00e9tico<\/b><\/span><\/span><\/span><\/p>\n

H<\/b><\/i><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>gr\u00e1fico <\/b><\/span><\/span><\/span>da <\/b><\/span><\/span><\/span>figura 1<\/b><\/span><\/span><\/span>\u00a0mostra a\u00a0<\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica\u00a0de determinado fio de\u00a0resistividade el\u00e9trica \u03c1 = 64,8.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\u00a0\u03a9m <\/b><\/span><\/span><\/span>em <\/b><\/span><\/span><\/span>fun\u00e7\u00e3o da\u00a0frequ\u00eancia\u00a0<\/b><\/span><\/span><\/span>f\u00a0<\/b><\/i><\/span><\/span><\/span>da <\/b><\/span><\/span><\/span>corrente el\u00e9trica alternada que circula por esse fio, para diferentes valores de\u00a0<\/b><\/span><\/span><\/span>H\u00a0<\/b><\/i><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

a) <\/b><\/span><\/span><\/span>Como podemos ver <\/b><\/span><\/span><\/span>na figura 1,<\/b><\/span><\/span><\/span> o valor da <\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica do fio para\u00a0<\/b><\/span><\/span><\/span>f\u00a0<\/b><\/i><\/span><\/span><\/span>= 0 Hz \u00e9\u00a0<\/b><\/span><\/span><\/span>R = <\/b><\/i><\/span><\/span><\/span>1,5 \u2126. Calcule <\/b><\/span><\/span><\/span>o\u00a0<\/b><\/span><\/span><\/span>comprimento\u00a0<\/b><\/span><\/span><\/span>L\u00a0<\/b><\/i><\/span><\/span><\/span>desse fio, <\/b><\/span><\/span><\/span>cuja\u00a0<\/b><\/span><\/span><\/span>\u00e1rea de se\u00e7\u00e3o transversal vale\u00a0<\/b><\/span><\/span><\/span>A = <\/b><\/i><\/span><\/span><\/span>1,296 10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Para <\/b><\/span><\/span><\/span>altas frequ\u00eancias, <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>corrente el\u00e9trica alternada n\u00e3o est\u00e1 uniformemente distribu\u00edda na se\u00e7\u00e3o reta do fio, <\/b><\/span><\/span><\/span>mas sim <\/b><\/span><\/span><\/span>confinada em uma regi\u00e3o pr\u00f3xima a sua superf\u00edcie. <\/b><\/span><\/span><\/span><\/p>\n

Esta <\/b><\/span><\/span><\/span>regi\u00e3o <\/b><\/span><\/span><\/span>\u00e9 determinada pelo <\/b><\/span><\/span><\/span>comprimento de penetra\u00e7\u00e3o,<\/b><\/span><\/span><\/span> que \u00e9 dado <\/b><\/span><\/span><\/span>por\u00a0\"\"=k\u221a(\u03c1\/\u03bc<\/b><\/span><\/span><\/span>r<\/b><\/span><\/span><\/sub><\/span>.f),<\/b><\/span><\/span><\/span> em que <\/b><\/span><\/span><\/span>\u03c1 <\/b><\/span><\/span><\/span>\u00e9 a <\/b><\/span><\/span><\/span>resistividade do fio,\u00a0<\/b><\/span><\/span><\/span>f\u00a0<\/b><\/i><\/span><\/span><\/span>\u00e9 a <\/b><\/span><\/span><\/span>frequ\u00eancia da corrente el\u00e9trica alternada, \u03bc<\/b><\/span><\/span><\/span>r<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span>\u00e9 a <\/b><\/span><\/span><\/span>permeabilidade magn\u00e9tica relativa do fio e k=500\u221a(mHz\/\u2126).<\/b><\/span><\/span><\/span><\/p>\n

Sabendo que <\/b><\/span><\/span><\/span>\u03bc<\/b><\/span><\/span><\/span>r<\/b><\/span><\/span><\/sub><\/span>\u00a0varia com o\u00a0campo magn\u00e9tico aplicado\u00a0<\/b><\/span><\/span><\/span>H\u00a0<\/b><\/i><\/span><\/span><\/span>, como <\/b><\/span><\/span><\/span>mostra a figura 2, <\/b><\/span><\/span><\/span>e que, para o<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

particular valor de f = 8M Hz temos\u00a0<\/b><\/span><\/span><\/span>R <\/b><\/i><\/span><\/span><\/span>\u2248 4\u2126, calcule o valor de\u00a0\"\"para essa situa\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

12-(CEDERJ-RJ)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>circuito mostra\u00a0tr\u00eas elementos resistivos <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>resist\u00eancias\u00a0R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span>ligados a uma <\/b><\/span><\/span><\/span>fonte de tens\u00e3o V<\/b><\/span><\/span><\/span>\u00a0por <\/b><\/span><\/span><\/span>fios condutores de resist\u00eancia desprez\u00edvel<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>valores das\u00a0diferen\u00e7as de potencial\u00a0<\/b><\/span><\/span><\/span>entre os <\/b><\/span><\/span><\/span>terminais desses resistores e das\u00a0correntes el\u00e9tricas que fluem atrav\u00e9s deles\u00a0<\/b><\/span><\/span><\/span>s\u00e3o, respectivamente,\u00a0<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0= 8,0V e I<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0= 4,0A, V<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0= 4,0V e I<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2,0A, V<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0= 4,0V e I<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2,0A.<\/b><\/span><\/span><\/span><\/p>\n

Assinale a <\/b><\/span><\/span><\/span>alternativa que descreve corretamente <\/b><\/span><\/span><\/span>a\u00a0<\/b><\/span><\/span><\/span>compara\u00e7\u00e3o<\/b><\/span><\/span><\/span> entre as <\/b><\/span><\/span><\/span>resist\u00eancias\u00a0R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span>e entre\u00a0as <\/b><\/span><\/span><\/span>pot\u00eancias dissipadas, respectivamente, pelo resistor R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0(pot\u00eancia P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>) e pelo conjunto\u00a0formado por R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0(pot\u00eancia P<\/b><\/span><\/span><\/span>23<\/b><\/span><\/span><\/sub><\/span>).<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

13-(UERJ-RJ)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

No <\/b><\/span><\/span><\/span>circuito,<\/b><\/span><\/span><\/span> uma <\/b><\/span><\/span><\/span>bateria B <\/b><\/span><\/span><\/span>est\u00e1 <\/b><\/span><\/span><\/span>conectada a tr\u00eas resistores de resist\u00eancias R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>:<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Sabe-se que R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0= R<\/b><\/span><\/span><\/span>3 <\/b><\/span><\/span><\/sub><\/span>= 2R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>rela\u00e7\u00e3o entre as pot\u00eancias P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e P<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>respectivamente <\/b><\/span><\/span><\/span>associadas a R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>. R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>pode ser <\/b><\/span><\/span><\/span>expressa<\/b><\/span><\/span><\/span> como:<\/b><\/span><\/span><\/span><\/p>\n

(A) <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

(B) <\/b><\/span><\/span><\/span>2P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

(C) <\/b><\/span><\/span><\/span>4P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

(D) <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>= 2P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>= 2P<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span><\/p>\n

14-(MACKENZIE-SP)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

No <\/b><\/span><\/span><\/span>circuito desenhado<\/b><\/span><\/span><\/span>, a\u00a0<\/b><\/span><\/span><\/span>intensidade de corrente el\u00e9trica\u00a0<\/b><\/span><\/span><\/span>cont\u00ednua que <\/b><\/span><\/span><\/span>passa pelo\u00a0resistor de 50 \u03a9\u00a0\u00e9 de 80 mA. <\/b><\/span><\/span><\/span>A\u00a0<\/b><\/span><\/span><\/span>for\u00e7a eletromotriz\u00a0\u03b5\u00a0do gerador\u00a0ideal<\/b><\/span><\/span><\/span> \u00e9 igual a<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>1,5 V <\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>3,0 V <\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>4,5 V <\/b><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span>5,0 V <\/b><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>6,0 V<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

Duas pilhas el\u00e9tricas <\/b><\/span><\/span><\/span>de\u00a0<\/b><\/span><\/span><\/span>resist\u00eancias internas\u00a0nulas, <\/b><\/span><\/span><\/span>associadas <\/b><\/span><\/span><\/span>em\u00a0s\u00e9rie,\u00a0\u201calimentam\u201d <\/b><\/span><\/span><\/span>a\u00a0<\/b><\/span><\/span><\/span>l\u00e2mpada<\/b><\/span><\/span><\/span><\/p>\n

incandescente\u00a0ilustrada <\/b><\/span><\/span><\/span>na figura ao abaixo.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span><\/span>amper\u00edmetro ideal A\u00a0<\/b><\/span><\/span><\/span>indica a <\/b><\/span><\/span><\/span>intensidade de\u00a0corrente el\u00e9trica 0,50 A, <\/b><\/span><\/span><\/span>quando o\u00a0<\/b><\/span><\/span><\/span>volt\u00edmetro V, tamb\u00e9m ideal,<\/b><\/span><\/span><\/span> indica a\u00a0<\/b><\/span><\/span><\/span>d.d.p. de 3,00 V. <\/b><\/span><\/span><\/span><\/p>\n

Sabendo-se que a\u00a0<\/b><\/span><\/span><\/span>pot\u00eancia dissipada\u00a0por efeito Joule no filamento da l\u00e2mpada<\/b><\/span><\/span><\/span> corresponde a\u00a0<\/b><\/span><\/span><\/span>1\/4 <\/b><\/span><\/span><\/span>do <\/b><\/span><\/span><\/span>valor nominal, indicado pelo fabricante, <\/b><\/span><\/span><\/span>pode-se afirmar que os\u00a0<\/b><\/span><\/span><\/span>valores m\u00e1ximos<\/b><\/span><\/span><\/span> nominais, de\u00a0<\/b><\/span><\/span><\/span>pot\u00eancia e tens\u00e3o el\u00e9trica especificados na l\u00e2mpada\u00a0(pot\u00eancia \u2014 d.d.p.),\u00a0<\/b><\/span><\/span><\/span>s\u00e3o<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span><\/span>1,50 W \u2014 3,00 V <\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span><\/span>3,00 W \u2014 3,00 V <\/b><\/span><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span><\/span>3,00 W \u2014 6,00 V <\/b><\/span><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span><\/span><\/span>6,00 W \u2014 6,00 V<\/b><\/span><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span><\/span>6,00 W \u2014 3,00 V<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

\"\"<\/p>\n

Na <\/b><\/span><\/span><\/span>associa\u00e7\u00e3o de resistores ao lado, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>s\u00edmbolo<\/b><\/span><\/span><\/span>\u00a0\"\"\u00a0representa um\u00a0<\/b><\/span><\/span><\/span>resistor\u00a0cuja resist\u00eancia el\u00e9trica \u00e9\u00a0R ohm.<\/b><\/span><\/span><\/span> Calculando a\u00a0<\/b><\/span><\/span><\/span>resist\u00eancia equivalente\u00a0dessa associa\u00e7\u00e3o, entre os pontos\u00a0A e D, <\/b><\/span><\/span><\/span>obteremos:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>R\/2 <\/b><\/span><\/span><\/span>b) <\/b><\/span><\/span><\/span>3R\/2 <\/b><\/span><\/span><\/span>c) <\/b><\/span><\/span><\/span>9R\/4 <\/b><\/span><\/span><\/span>d) <\/b><\/span><\/span><\/span>3R\/12 <\/b><\/span><\/span><\/span>e) <\/b><\/span><\/span><\/span>3R\/16<\/b><\/span><\/span><\/span><\/p>\n

17-(UEL-PR)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

No <\/b><\/span><\/span><\/span>circuito ao lado, <\/b><\/span><\/span><\/span>sabe-se que\u00a0<\/b><\/span><\/span><\/span>\u03b5<\/b><\/i><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2<\/b><\/span><\/span><\/span>\u03b5<\/b><\/i><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span>e que <\/b><\/span><\/span><\/span>ambas s\u00e3o for\u00e7as eletromotrizes (fem) ideais.<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Determine a\u00a0<\/b><\/span><\/span><\/span>diferen\u00e7a de potencial entre os pontos\u00a0<\/b><\/span><\/span><\/span>a\u00a0<\/b><\/i><\/span><\/span><\/span>e\u00a0<\/b><\/span><\/span><\/span>b\u00a0<\/b><\/i><\/span><\/span><\/span>pelo ramo da direita do circuito.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Determine o\u00a0<\/b><\/span><\/span><\/span>valor da corrente\u00a0<\/b><\/span><\/span><\/span>i<\/b><\/i><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

Apresente os c\u00e1lculos<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

18-(UFJF-MG)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>estudante de f\u00edsica, <\/b><\/span><\/span><\/span>com o <\/b><\/span><\/span><\/span>intuito de testar algumas teorias <\/b><\/span><\/span><\/span>sobre <\/b><\/span><\/span><\/span>circuitos e indu\u00e7\u00e3o eletromagn\u00e9tica, <\/b><\/span><\/span><\/span>montou o <\/b><\/span><\/span><\/span>circuito el\u00e9trico indicado na figura abaixo.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

O <\/b><\/span><\/span><\/span>circuito \u00e9 composto de quatro resistores <\/b><\/span><\/span><\/span>com <\/b><\/span><\/span><\/span>resist\u00eancias el\u00e9tricas R = 5k\u2126 id\u00eanticas<\/b><\/span><\/span><\/span>, uma <\/b><\/span><\/span><\/span>chave<\/b><\/span><\/span><\/span> <\/b>S,<\/b><\/span><\/span><\/span> uma <\/b><\/span><\/span><\/span>fonte de fem \u03b5 = 150V <\/b><\/span><\/span><\/span>e um <\/b><\/span><\/span><\/span>fio muito longo. <\/b><\/span><\/span><\/span><\/p>\n

Pr\u00f3ximo a esse fio se encontra uma bobina B <\/b><\/span><\/span><\/span>no plano da p\u00e1gina, <\/b><\/span><\/span><\/span>ligada a um amper\u00edmetro A, <\/b><\/span><\/span><\/span>capaz de <\/b><\/span><\/span><\/span>medir a corrente induzida na bobina. <\/b><\/span><\/span><\/span>Com <\/b><\/span><\/span><\/span>base nessas informa\u00e7\u00f5es, <\/b><\/span><\/span><\/span>fa\u00e7a o que se <\/b><\/span><\/span><\/span>pede:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span>Calcule a <\/b><\/span><\/span><\/span>corrente no circuito antes da chave S ser fechada.<\/b><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span><\/span>Calcule a <\/b><\/span><\/span><\/span>corrente no circuito ap\u00f3s a chave S ser fechada.<\/b><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span><\/span>A corrente <\/b><\/span><\/span><\/span>induzida na bobina imediatamente ap\u00f3s a chave S ser fechada ter\u00e1 o mesmo sentido da corrente no circuito? Justifique sua resposta.<\/b><\/span><\/span><\/span><\/p>\n

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

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

\"\"<\/p>\n

Considere o\u00a0<\/b><\/span><\/span><\/span>circuito formado por tr\u00eas l\u00e2mpadas id\u00eanticas <\/b><\/span><\/span><\/span>ligadas em <\/b><\/span><\/span><\/span>paralelo \u00e0 bateria, <\/b><\/span><\/span><\/span>conforme representa\u00a0a <\/b><\/span><\/span><\/span>figura (1).<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Como a\u00a0<\/b><\/span><\/span><\/span>chave C foi\u00a0aberta na figura (2),\u00a0<\/b><\/span><\/span><\/span>considere as <\/b><\/span><\/span><\/span>afirma\u00e7\u00f5es abaixo\u00a0sobre a figura (2)<\/b><\/span><\/span><\/span>, em <\/b><\/span><\/span><\/span>compara\u00e7\u00e3o \u00e0 situa\u00e7\u00e3o descrita na figura (1).<\/b><\/span><\/span><\/span><\/p>\n

I – <\/b><\/span><\/span><\/span>A <\/b><\/span><\/span><\/span>pot\u00eancia fornecida pela bateria \u00e9 a mesma.<\/b><\/span><\/span><\/span><\/p>\n

II – <\/b><\/span><\/span><\/span>A <\/b><\/span><\/span><\/span>diferen\u00e7a de potencial <\/b><\/span><\/span><\/span>aplicada <\/b><\/span><\/span><\/span>a cada l\u00e2mpada acesa \u00e9 a mesma.<\/b><\/span><\/span><\/span><\/p>\n

III – <\/b><\/span><\/span><\/span>As <\/b><\/span><\/span><\/span>correntes el\u00e9tricas que percorrem as l\u00e2mpadas acesas s\u00e3o menores.<\/b><\/span><\/span><\/span><\/p>\n

Quais <\/b><\/span><\/span><\/span>est\u00e3o corretas?<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

\"\"<\/p>\n

21-(ENEM-MEC-016)<\/span><\/span><\/span>
\n\"\"<\/b><\/span><\/span><\/span><\/p>\n

Por <\/b><\/span><\/span><\/span>apresentar significativa resistividade el\u00e9trica<\/b><\/span><\/span><\/span>, o <\/b><\/span><\/span><\/span>grafite<\/b><\/span><\/span><\/span> pode ser utilizado para <\/b><\/span><\/span><\/span>simular resistoresel\u00e9tricos em circuitos desenhados no papel,<\/b><\/span><\/span><\/span> com o uso de <\/b><\/span><\/span><\/span>l\u00e1pis e lapiseiras.<\/b><\/span><\/span><\/span><\/p>\n

Dependendo da <\/b><\/span><\/span><\/span>espessura e do comprimento das linhas desenhadas<\/b><\/span><\/span><\/span>, \u00e9 poss\u00edvel <\/b><\/span><\/span><\/span>determinar <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica de cada tra\u00e7ado produzido.<\/b><\/span><\/span><\/span><\/p>\n

No <\/b><\/span><\/span><\/span>esquema foram utilizados tr\u00eas tipos de l\u00e1pis diferentes (2H, HB e 6B)<\/b><\/span><\/span><\/span> para efetuar <\/b><\/span><\/span><\/span>tr\u00eas tra\u00e7ados<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

Munida dessas informa\u00e7\u00f5es,<\/b><\/span><\/span><\/span> um estudante <\/b><\/span><\/span><\/span>pegou <\/b><\/span><\/span><\/span>uma <\/b><\/span><\/span><\/span>folha depapel<\/b><\/span><\/span><\/span> e fez o <\/b><\/span><\/span><\/span>desenho de um sorvetede casquinha utilizando-se desses tra\u00e7ados. <\/b><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>valores <\/b><\/span><\/span><\/span>encontrados nesse <\/b><\/span><\/span><\/span>experimento,<\/b><\/span><\/span><\/span> para as <\/b><\/span><\/span><\/span>resist\u00eancias el\u00e9tricas (R),<\/b><\/span><\/span><\/span> medidas com o <\/b><\/span><\/span><\/span>aux\u00edlio de um ohm\u00edmetro ligado<\/b><\/span><\/span><\/span> nas <\/b><\/span><\/span><\/span>extremidades das resist\u00eancias, s\u00e3o mostrados na figura.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Verificou-se<\/b><\/span><\/span><\/span> que os <\/b><\/span><\/span><\/span>resistores obedeciam a Lei de Ohm.<\/b><\/span><\/span><\/span><\/p>\n

Na <\/b><\/span><\/span><\/span>sequ\u00eancia, conectou o ohm\u00edmetro nos terminais A e B<\/b><\/span><\/span><\/span> do <\/b><\/span><\/span><\/span>desenho<\/b><\/span><\/span><\/span> e, em seguida, <\/b><\/span><\/span><\/span>conectou-o nos terminais B e C, <\/b><\/span><\/span><\/span>anotando as <\/b><\/span><\/span><\/span>leituras R<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span>\u00a0e R<\/b><\/span><\/span><\/span>BC<\/b><\/span><\/span><\/sub><\/span>, respectivamente.<\/b><\/span><\/span><\/span><\/p>\n

Ao <\/b><\/span><\/span><\/span>estabelecer a raz\u00e3o R<\/b><\/span><\/span><\/span>AB<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>BC <\/b><\/span><\/span><\/sub><\/span>qual resultado o estudante obteve?<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

 <\/p>\n

Confira as resolu\u00e7\u00f5es comentadas e gabaritos<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Racioc\u00ednio L\u00f3gico ELETRODIN\u00c2MICA Como esse conte\u00fado envolve muita teoria, em caso de d\u00favidas voc\u00ea pode encontr\u00e1-la em\u00a0fisicaevestibular.com.br \u2013 Eletrodin\u00e2mica 01-(UNIFESP-SP) Para compor sua decora\u00e7\u00e3o de Natal, um comerciante decide construir uma estrela para pendurar na fachada de sua loja. Para isso, utilizar\u00e1 um material que, quando\u00a0percorrido por corrente el\u00e9trica, brilhe emitindo luz colorida.\u00a0 Ele tem \u00e0 sua disposi\u00e7\u00e3o\u00a0barras de diferentes<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2508,"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-2892","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2892","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=2892"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2892\/revisions"}],"predecessor-version":[{"id":2898,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2892\/revisions\/2898"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2508"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2892"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}