{"id":1670,"date":"2015-12-19T15:17:54","date_gmt":"2015-12-19T15:17:54","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=1670"},"modified":"2024-08-20T11:07:39","modified_gmt":"2024-08-20T11:07:39","slug":"resolucao-comentada-das-questoes-de-vestibulares-sobre-o-conteudo-condutor-em-equilibrio-eletrostatico-blindagem-eletrostatica","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/eletricidade\/eletrostatica\/1664-2\/resolucao-comentada-das-questoes-de-vestibulares-sobre-o-conteudo-condutor-em-equilibrio-eletrostatico-blindagem-eletrostatica\/","title":{"rendered":"Blindagem eletrost\u00e1tica – Resolu\u00e7\u00e3o"},"content":{"rendered":"

Resolu\u00e7\u00e3o comentada das quest\u00f5es de vestibulares sobre o conte\u00fado<\/b><\/span><\/span><\/span> <\/b>Condutor em equil\u00edbrio eletrost\u00e1tico \u2013 Blindagem eletrost\u00e1tica<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

01-<\/b><\/span><\/span><\/span> R- D<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

02-<\/b><\/span><\/span><\/span> R- B<\/b><\/span><\/span><\/span><\/p>\n

03-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A descarga el\u00e9trica ocorrida ir\u00e1 eletrizar o avi\u00e3o\u00a0 —\u00a0 por\u00e9m, como sua fuselagem \u00e9 met\u00e1lica (bom condutor), essas cargas ir\u00e3o se distribuir na superf\u00edcie externa, n\u00e3o causando danos aos passageiros. A fuselagem atua como blindagem para o seu conte\u00fado.<\/b><\/span><\/span><\/span><\/p>\n

R- D<\/b><\/span><\/span><\/span><\/p>\n

04-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>(01) Falsa\u00a0 —\u00a0 a eletriza\u00e7\u00e3o ocorre por atrito.<\/b><\/span><\/span><\/span><\/p>\n

(02) Verdadeira\u00a0 —\u00a0 as cargas el\u00e9tricas ficam distribu\u00eddas pela superf\u00edcie do condutor, seja ele oco ou maci\u00e7o (blindagem eletrost\u00e1tica), e consequentemente, o campo el\u00e9trico no seu interior \u00e9 nulo.<\/b><\/span><\/span><\/span><\/p>\n

(04) Falsa\u00a0 —\u00a0 os isolantes tamb\u00e9m podem ser eletrizados por atrito.<\/b><\/span><\/span><\/span><\/p>\n

(08) Verdadeira\u00a0 —\u00a0 o campo el\u00e9trico criado nas partes pontiagudas de um condutor eletrizado, pode assumir valores extremamente altos e provocar um fen\u00f4meno eletrost\u00e1tico denominado poder das pontas, que consiste na troca de cargas el\u00e9tricas entre as pontas do corpo eletrizado e o meio isolante que o envolve.<\/b><\/span><\/span><\/span><\/p>\n

(16) Falsa\u00a0 — o potencial el\u00e9trico \u00e9 o mesmo em todos os pontos da superf\u00edcie de um condutor em equil\u00edbrio eletrost\u00e1tico, portanto a superf\u00edcie \u00e9 eq\u00fcipotencial.<\/b><\/span><\/span><\/span><\/p>\n

(32) Verdadeira Internamente o potencial el\u00e9trico \u00e9 constante e igual ao potencial na superf\u00edcie.<\/b><\/span><\/span><\/span><\/p>\n

R- (02 + 08 + 32)=<\/b><\/span><\/span><\/span>42<\/b><\/span><\/span><\/span><\/p>\n

05-<\/b><\/span><\/span><\/span> R- (02+04+16)=22
\n<\/b><\/span><\/span><\/span><\/p>\n

06-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>I. Verdadeira\u00a0 —\u00a0 todos os pontos internos e da superf\u00edcie possuem o mesmo potencial.<\/b><\/span><\/span><\/span><\/p>\n

II. Falsa\u00a0 —\u00a0 \u00e9 mais intenso em B (ponta)<\/b><\/span><\/span><\/span><\/p>\n

III. Verdadeira<\/b><\/span><\/span><\/span><\/p>\n

R- D<\/b><\/span><\/span><\/span><\/p>\n

07-<\/b><\/span><\/span><\/span> R- C\u00a0\u00a0<\/b><\/span><\/span><\/span>—\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

08-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>O campo el\u00e9trico \u00e9 mais intenso onde existir maior densidade de carga o que acontece nas pontas (nos v\u00e9rtices), onde o raio de curvatura \u00e9 menor.<\/b><\/span><\/span><\/span><\/p>\n

R- C<\/b><\/span><\/span><\/span><\/p>\n

09-<\/b><\/span><\/span><\/span> R- D<\/b><\/span><\/span><\/span><\/p>\n

10-<\/b><\/span><\/span><\/span> R- D\u00a0\u00a0<\/b><\/span><\/span><\/span>—\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

11-<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>Se uma penitenci\u00e1ria fosse envolvida por uma malha met\u00e1lica, onde os \u201cburacos\u201d tivessem dimens\u00f5es menores de 15 cm, n\u00e3o haveria a penetra\u00e7\u00e3o de campos el\u00e9tricos em seu interior, tornando-a blindada a ondas eletromagn\u00e9ticas na faixa da telefonia m\u00f3vel (da ordem de 1.800MHz). No entanto, isso n\u00e3o \u00e9 feito pelo alto custo, preferindo-se a utiliza\u00e7\u00e3o da interfer\u00eancia, emitindo-se ondas nessa faixa de freq\u00fc\u00eancia com intensidade muito maior.<\/b><\/span><\/span><\/span><\/p>\n

R- E<\/b><\/span><\/span><\/span><\/p>\n

12-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Falsa\u00a0 —\u00a0 a carga induzida na esfera maior estar\u00e1 distribu\u00edda pela sua superf\u00edcie externa, havendo maior concentra\u00e7\u00e3o pr\u00f3xima da esfera menor.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b) Verdadeira\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

c) Falsa\u00a0 —\u00a0 no interior da esfera maior, o campo el\u00e9trico ser\u00e1 n\u00e3o-nulo devido \u00e0 carga \u2013Q da esfera menor e, na parte externa, o campo el\u00e9trico ser\u00e1 tamb\u00e9m n\u00e3o-nulo, devido \u00e0 carga \u2013Q e \u00e0 carga +Q (induzida na superf\u00edcie externa da esfera maior).<\/b><\/span><\/span><\/span><\/p>\n

d) Falsa\u00a0 —\u00a0 se o fio condutor, a carga \u2013Q ir\u00e1 para a superf\u00edcie externa da esfera maior, proporcionando um campo el\u00e9trico nulo na parte interna dessa esfera.<\/b><\/span><\/span><\/span><\/p>\n

R- B<\/b><\/span><\/span><\/span><\/p>\n

13-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Nas pontas de um condutor eletrizado, encontramos uma quantidade maior de cargas por unidade de \u00e1rea.<\/b><\/span><\/span><\/span><\/p>\n

R- A<\/b><\/span><\/span><\/span><\/p>\n

14-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>O campo el\u00e9trico \u00e9 nulo nos pontos internos de um condutor eletrizado e em equil\u00edbrio, independentemente da sua forma.<\/b><\/span><\/span><\/span><\/p>\n

R- E<\/b><\/span><\/span><\/span><\/p>\n

15-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>01. Correta\u00a0 —\u00a0 com S<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0ligada, cargas el\u00e9tricas negativas do gerador fluir\u00e3o at\u00e9 a esfera condutora maci\u00e7a eletrizando-a, que por sua vez induzir\u00e3o cargas positivas na superf\u00edcie externa da casca esf\u00e9rica condutora que tamb\u00e9m induzir\u00e3o cargas no p\u00eandulo, que continua neutro, atraindo-o por indu\u00e7\u00e3o el\u00e9trica.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

02. Correta\u00a0 —\u00a0 veja em fisicaevestibular o processo de eletriza\u00e7\u00e3o por indu\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

04- Falsa \u00a0—\u00a0 a casca esf\u00e9rica eletrizada origina campo el\u00e9trico ao seu redor.<\/b><\/span><\/span><\/span><\/p>\n

08. Correta\u00a0 —\u00a0 veja 02<\/b><\/span><\/span><\/span><\/p>\n

16- Falsa\u00a0 —\u00a0 veja 01<\/b><\/span><\/span><\/span><\/p>\n

R- (01 + 02 + 08)=11<\/b><\/span><\/span><\/span><\/p>\n

16-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>d=Q\/S\u00a0 —\u00a0 d=Q\/4\u03c0R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>=Q\/4\u03c0(5.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q=10<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.\u03c0.1<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q=\u03c0.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- A<\/b><\/span><\/span><\/span><\/p>\n

17-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Sendo o raio da esfera de 0,5m=50cm, o ponto distante 30cm do centro da esfera est\u00e1 em seu interior\u00a0 —\u00a0 E=0\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- D<\/b><\/span><\/span><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

18-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) E=KQ\/d<\/b><\/span><\/span><\/span>2+<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0 9.10<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sup><\/span>=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.Q\/4\u00a0 —\u00a0 Q=4,0.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 b) n\u00e3o \u00e9 nulo, \u00e9 constante e diferente de zero\u00a0 —\u00a0 c) V=KQ\/R=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

4.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>\/1\u00a0 —\u00a0 V=36.10<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sup><\/span>V\u00a0 —\u00a0 d) V=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.4.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>\/4\u00a0 —\u00a0 V=9.10<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sup><\/span>V\u00a0 —\u00a0 e) E=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.4.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>\/9\u00a0 —\u00a0 E=4,0.10<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sup><\/span>N\/C<\/b><\/span><\/span><\/span><\/p>\n

R- E<\/b><\/span><\/span><\/span><\/p>\n

19-<\/b><\/span><\/span><\/span> R- D<\/b><\/span><\/span><\/span><\/p>\n

20-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=KQ<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 9=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\/10.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\/Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=R<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=10.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\/5.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=2Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0+ Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>= Q\u2019<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0+ Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>\u00a0+ 0 = 2Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0+ Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>\/3\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=0,33.10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=0,66.10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- A<\/b><\/span><\/span><\/span><\/p>\n

21-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Essa rigidez equivale ao campo el\u00e9trico pr\u00f3ximo da esfera\u00a0 —\u00a0 \u00a0E<\/b><\/span><\/span><\/span>pr\u00f3ximo<\/b><\/span><\/span><\/sub><\/span>=3.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>N\/C\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>pr\u00f3ximo<\/b><\/span><\/span><\/sub><\/span>=KQ\/R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>pr\u00f3ximo<\/b><\/span><\/span><\/sub><\/span>=E<\/b><\/span><\/span><\/span>superf\u00edcie<\/b><\/span><\/span><\/sub><\/span>\/2\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>superf\u00edcie<\/b><\/span><\/span><\/sub><\/span>=2 E<\/b><\/span><\/span><\/span>pr\u00f3ximo<\/b><\/span><\/span><\/sub><\/span>\u00a0\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>superf\u00ede<\/b><\/span><\/span><\/sub><\/span>=2.3.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>=6.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>N\/C\u00a0 —\u00a0 6.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.Q\/(3.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u00a06.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>Q\/9.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q=6.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\/10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q=6.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\/10<\/b><\/span><\/span><\/span>11<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q=6.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>C ou<\/b><\/span><\/span><\/span>\u00a0Q=60\u03bcC<\/b><\/span><\/span><\/span><\/p>\n

b) V=KQ\/R=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.6.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>\/3.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 V=18.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>V ou\u00a0<\/b><\/span><\/span><\/span>V=1,8MV
\n<\/b><\/span><\/span><\/span><\/p>\n

22-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Q<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=4.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/Q\u2019<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/Q\u2019<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=5.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\/15.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/Q\u2019<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=3\u00a0 — Q\u2019<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=3Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 Q<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0+ Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>= Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0+ Q\u2019<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 4.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0+ 0 = Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0+ 3Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 4 Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=4.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 Q\u2019<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=3.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —<\/b><\/span><\/span><\/span>\u00a0 R- D<\/b><\/span><\/span><\/span><\/p>\n

23-<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

24-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Na pequen\u00edssima esfera (ordem de micr\u00f4metros)\u00a0 —\u00a0 R=10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>m\u00a0 —\u00a0 S = 4pR<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0= 4.3.(10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=12.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0isto significa que \u00e9 da ordem de 10<\/b><\/span><\/span><\/span>-11<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>2\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 Q = 10.000.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>\u00a0= 1,6.10<\/b><\/span><\/span><\/span>-15<\/b><\/span><\/span><\/sup><\/span>\u00a0C\u00a0 —\u00a0 \u00a0isto significa da ordem de 10<\/b><\/span><\/span><\/span>-15<\/b><\/span><\/span><\/sup><\/span>\u00a0C<\/b><\/span><\/span><\/span><\/p>\n

A densidade superficial de carga ser\u00e1\u00a0 —\u00a0 d=Q\/S = 10<\/b><\/span><\/span><\/span>-15<\/b><\/span><\/span><\/sup><\/span>C\/(10<\/b><\/span><\/span><\/span>-11<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>)\u00a0 —\u00a0 d=10<\/b><\/span><\/span><\/span>-4<\/b><\/span><\/span><\/sup><\/span>\u00a0C\/m<\/b><\/span><\/span><\/span>2\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 na pequena esfera (ordem de mil\u00edmetros)\u00a0 —\u00a0 R=10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>m<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 S = 4pR<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0= 4.3.(10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=12.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0 que significa da ordem de 10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 usando a densidade de carga anterior tem-se\u00a0 —\u00a0 Q=d.S=10<\/b><\/span><\/span><\/span>-4<\/b><\/span><\/span><\/sup><\/span>S=10<\/b><\/span><\/span><\/span>-4.<\/b><\/span><\/span><\/sup><\/span>.10<\/b><\/span><\/span><\/span>-5<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q=10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 o n\u00famero de cargas elementares dever\u00e1 ser da ordem de\u00a0 —\u00a0<\/b><\/span><\/span><\/span><\/p>\n

n = Q\/e = 10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\/(1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>) = 0,625.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>\u00a0= 6,25.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>\u00a0que tem ordem de grandeza em 10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>, visto que a parte significativa \u00e9 maior que a \u221a10=3,16\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- D<\/b><\/span><\/span><\/span><\/p>\n

25-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Em um condutor eletrizado o campo el\u00e9trico em seu interior \u00e9 nulo\u00a0 —\u00a0 o potencial el\u00e9trico no interior \u00e9 igual ao potencial el\u00e9trico na superf\u00edcie.<\/b><\/span><\/span><\/span><\/p>\n

R- B<\/b><\/span><\/span><\/span><\/p>\n

26-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Todo excesso de carga tender\u00e1 a repelir e ficar\u00e3o concentrados na superf\u00edcie da esfera\u00a0 externa\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- E<\/b><\/span><\/span><\/span><\/p>\n

27-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Q<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=2R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 Q<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=2Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 \u03c3<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=Q<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/S<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=2Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/4\u03c0R<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>2<\/b><\/span><\/span><\/sup><\/span>=2Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/4\u03c0(2R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u03c3<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/8\u03c0R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u03c3<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/4\u03c0R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u03c3<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/\u03c3<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/8\u03c0R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0X 4\u03c0R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/Q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0—\u00a0 \u03c3<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>=2 \u03c3<\/b><\/span><\/span><\/span>1\u00a0<\/b><\/span><\/span><\/sub><\/span>—\u00a0<\/b><\/span><\/span><\/span>\u00a0R- C<\/b><\/span><\/span><\/span><\/p>\n

28-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>00. Falsa\u00a0 —\u00a0 o potencial el\u00e9trico \u00e9 o mesmo, constante e diferente de zero, pois est\u00e3o ligados por um fio condutor.<\/b><\/span><\/span><\/span><\/p>\n

01. Falsa\u00a0 —\u00a0 \u00e9 o mesmo no interior e na superf\u00edcie.<\/b><\/span><\/span><\/span><\/p>\n

02. Verdadeira\u00a0 —\u00a0\u00a0 Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\/Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=R<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\/R<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=6\/2 —\u00a0 Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=3Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

04. Verdadeira\u00a0 —\u00a0\u00a0 Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>+ Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=8.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 3Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0+ Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=8.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=2.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 Q<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=6.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>C\u00a0 —\u00a0 V=KQ\/R=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.2.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\/2.<\/b><\/span><\/span><\/span><\/p>\n

10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.6.10<\/b><\/span><\/span><\/span>-8<\/b><\/span><\/span><\/sup><\/span>\/6.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 V=9.10<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>V<\/b><\/span><\/span><\/span><\/p>\n

29-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>01- Falsa\u00a0 —\u00a0 no contato a carga total do sistema ser\u00e1 +q e os potenciais das esferas condutoras na superf\u00edcie dever\u00e3o ser os mesmos\u00a0 —\u00a0 m + n = q\u00a0 —\u00a0 onde m e n s\u00e3o as cargas das duas esferas ap\u00f3s a separa\u00e7\u00e3o das mesmas\u00a0 —\u00a0 K<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.m\/R = k<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.n\/(2R)\u00a0 —\u00a0<\/b><\/span><\/span><\/span><\/p>\n

m = n\/(2)\u00a0 —\u00a0 n = 2.m\u00a0 —\u00a0 m + n = q\u00a0 —\u00a0 m + 2.m = q\u00a0\u00a0 —\u00a0 3.m = q\u00a0 —\u00a0 m = q\/3 e n = 2q\/3\u00a0 —\u00a0 desta forma a for\u00e7a entre as esferas\u00a0 —\u00a0 F = k<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.m.n\/a<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0= k<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.(4q<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/9)\/a<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0o que invalida a afirma\u00e7\u00e3o (01).<\/b><\/span><\/span><\/span><\/p>\n

02. Correta\u00a0 —\u00a0 as cargas s\u00e3o diretamente proporcionais aos raios das esferas.<\/b><\/span><\/span><\/span><\/p>\n

04. Falsa\u00a0 —\u00a0 ap\u00f3s o contato o potencial el\u00e9trico \u00e9 o mesmo.<\/b><\/span><\/span><\/span><\/p>\n

08. Correta\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

16. Correta\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

32. Falsa\u00a0 —\u00a0 no interior da esfera o potencial \u00e9 constante e diferente de zero e, assim a diferen\u00e7a de potencial \u00e9 nula. \u00a0<\/b><\/span><\/span><\/span><\/p>\n

R- (02 + 08 + 16) = 26<\/b><\/span><\/span><\/span><\/p>\n

30-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Dados: q = 4.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>\u00a0C\u00a0 —\u00a0 d = 0,2 m = 2.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>\u00a0m\u00a0 —\u00a0 k = 9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>\u00a0N.m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/C<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

a) O campo eletrost\u00e1tico gerado pela part\u00edcula no centro da esfera maci\u00e7a \u00e9 dado pela lei de Coulomb:<\/b><\/span><\/span><\/span><\/p>\n

E = kq\/r<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u00a0E = 9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.4.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>\/(2.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E = 9,0.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>\u00a0N\/C, no sentido indicado na Fig 1.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

b) Analisando a Fig 2\u00a0 —\u00a0 \u00a0como a esfera condutora est\u00e1 em equil\u00edbrio eletrost\u00e1tico, o vetor campo el\u00e9trico resultante no seu interior \u00e9 nulo. A part\u00edcula eletrizada induz cargas el\u00e9tricas negativas (\u2013) e positivas (+) na superf\u00edcie da esfera, gerando um outro<\/b><\/span><\/span><\/span><\/p>\n

campo el\u00e9trico no seu interior (\"\"), em sentido oposto ao campo da part\u00edcula, de modo a anular o campo el\u00e9trico resultante.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

31-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>O atrito da pele das pessoas com objetos isolantes (l\u00e3, flanela, papel, pl\u00e1stico) tornam a pele eletrizada\u00a0 —\u00a0 em dias normais, esse excesso de cargas \u00e9 descarregado no contato com o pr\u00f3prio ar\u00a0 —\u00a0 por\u00e9m, em dias secos, esse processo torna-se muito lento, acumulando cargas est\u00e1ticas\u00a0 —\u00a0 no contato com objetos, principalmente met\u00e1licos, ocorre uma brusca descarga, que \u00e9 o choque el\u00e9trico\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- B<\/b><\/span><\/span><\/span><\/p>\n

32-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>I. Falsa\u00a0 —\u00a0 s\u00f3 o campo el\u00e9trico \u00e9 nulo, o potencial el\u00e9trico \u00e9 constante e diferente de zero.<\/b><\/span><\/span><\/span><\/p>\n

II. Falsa\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>=E<\/b><\/span><\/span><\/span>pr\u00f3ximo<\/b><\/span><\/span><\/sub><\/span>\/2=V\/2R\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

III. Falsa\u00a0 —\u00a0 V=KQ\/2R<\/b><\/span><\/span><\/span><\/p>\n

IV. Correta\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>=KQ\/(2R)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=KQ\/4R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0(1)\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>=KQ\/2R (2)\u00a0 —\u00a0 comparando (1) com (2)\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>=V<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>\/2R<\/b><\/span><\/span><\/span><\/p>\n

R- B<\/b><\/span><\/span><\/span><\/p>\n

33-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>E=KQ\/d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.2.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>\/9.10<\/b><\/span><\/span><\/span>-4<\/b><\/span><\/span><\/sup><\/span>\u00a0— E=2,0.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>N\/C —\u00a0 F=KQq\/d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.2.10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>.5.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\/9.10<\/b><\/span><\/span><\/span>-4<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 F=1,0.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>N\u00a0 —\u00a0 V=KQ\/d=9.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>.2.<\/b><\/span><\/span><\/span><\/p>\n

10<\/b><\/span><\/span><\/span>-6<\/b><\/span><\/span><\/sup><\/span>\/3.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 V=6,0.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>\u00a0V\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- C<\/b><\/span><\/span><\/span><\/p>\n

34-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Falsa\u00a0 —\u00a0 W=q<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.(V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0\u2013 V<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>)\u00a0 —\u00a0 como o potencial \u00e9 constante em pontos interiores da esfera\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>=V<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 W=q<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.0 = 0<\/b><\/span><\/span><\/span><\/p>\n

b) Falsa\u00a0 —\u00a0 o trabalho realizado nessas condi\u00e7\u00f5es \u00e9 calculado como se toda carga Q estivesse no centro da esfera\u00a0 —\u00a0 W=q<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0\u2013 V<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>), com V=KQ\/d<\/b><\/span><\/span><\/span><\/p>\n

c) Falsa\u00a0 —\u00a0 a medida que ela vai sendo carregada o potencial vai aumentando<\/b><\/span><\/span><\/span><\/p>\n

d) Correta\u00a0 —\u00a0 d=Q\/S=Q\/4\u03c0R<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 Q e R s\u00e3o fornecidos pelo gr\u00e1fico.<\/b><\/span><\/span><\/span><\/p>\n

e) Falsa\u00a0 —\u00a0 o campo el\u00e9trico \u00e9 nulo no interior da esfera.<\/b><\/span><\/span><\/span><\/p>\n

R- D<\/b><\/span><\/span><\/span><\/p>\n

35-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>No interior de um condutor (caixa met\u00e1lica) em equil\u00edbrio eletrost\u00e1tico, as cargas distribuem-se na superf\u00edcie externa do condutor, anulando o campo el\u00e9trico no seu interior. Esse fen\u00f4meno \u00e9 conhecido como blindagem eletrost\u00e1tica.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

R- B<\/b><\/span><\/span><\/span><\/p>\n

36-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Capacit\u00e2ncia C\u00a0 —\u00a0 C = \u03b5<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0A\/d = 9.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>.5.10<\/b><\/span><\/span><\/span>-4<\/b><\/span><\/span><\/sup><\/span>\/2.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 C = 2,25.10<\/b><\/span><\/span><\/span>-12\u00a0<\/b><\/span><\/span><\/sup><\/span>F\u00a0 —\u00a0 diferen\u00e7a de potencial V entre o rolo e a fita\u00a0 —\u00a0<\/b><\/span><\/span><\/span><\/p>\n

V=Q\/C=4,5.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\/2,25.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 V=2.0.10<\/b><\/span><\/span><\/span>3\u00a0<\/b><\/span><\/span><\/sup><\/span>V\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- C<\/b><\/span><\/span><\/span><\/p>\n

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

37-<\/b><\/span><\/span><\/span> I. Falsa\u00a0 —\u00a0 essa for\u00e7a \u00e9 fornecida por F=KQq\/d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0e K \u00e9 uma constante que depende do meio onde as cargas est\u00e3o imersas.<\/b><\/span><\/span><\/span><\/p>\n

II. Correta\u00a0 —\u00a0 depois do contato o bast\u00e3o neutro ficou com carga positiva, ou seja, perdeu el\u00e9trons.<\/b><\/span><\/span><\/span><\/p>\n

III. Falsa\u00a0 —\u00a0 s\u00f3 se eletrizam se forem de materiais diferentes e na eletriza\u00e7\u00e3o por atrito ter\u00e3o sempre cargas de mesmo m\u00f3dulo mas sinais contr\u00e1rios.<\/b><\/span><\/span><\/span><\/p>\n

IV. Correta\u00a0 —\u00a0 Define-se superf\u00edcie equipotencial de um campo el\u00e9trico a qualquer superf\u00edcie em cujos pontos o potencial el\u00e9trico \u00e9 constante.<\/b><\/span><\/span><\/span><\/p>\n

Estas superf\u00edcies t\u00eam duas propriedades importantes:
\n1<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0– A for\u00e7a el\u00e9trica durante o deslocamento de uma carga el\u00e9trica puntiforme sobre uma superf\u00edcie equipotencial \u00e9 nula.<\/b><\/span><\/span><\/span><\/p>\n

2<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0– As superf\u00edcies equipotenciais s\u00e3o perpendiculares \u00e0s linhas de for\u00e7a ou linhas de campo el\u00e9trico e, conseq\u00fcentemente, perpendiculares ao vetor campo el\u00e9trico e \u00e0 qualquer ponto da superf\u00edcie.\u00a0.<\/b><\/span><\/span><\/span><\/p>\n

V. Falsa\u00a0 —\u00a0 o campo el\u00e9trico em seu interior \u00e9 nulo\u00a0 —\u00a0 \u00e9 o potencial el\u00e9trico que \u00e9 constante.<\/b><\/span><\/span><\/span><\/p>\n

R- A<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

38-<\/b><\/span><\/span><\/span> Campo e potencial el\u00e9trico de um condutor esf\u00e9rico:<\/b><\/span><\/span><\/span><\/p>\n

Leia atentamente as informa\u00e7\u00f5es abaixo:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

01. Correta.<\/b><\/span><\/span><\/span><\/p>\n

02. Falsa\u00a0 —\u00a0 \u00e9 inversamente proporcional a D<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

04. Correta\u00a0 — \u00a0A densidade el\u00e9trica superficial (\u03c3) mede a concentra\u00e7\u00e3o de carga el\u00e9trica (Q) pela superf\u00edcie (\u00e1rea S)\u00a0 — \u00a0\u03c3=Q\/S\u00a0 —\u00a0 no caso de esfera de raio R, a \u00e1rea da superf\u00edcie esf\u00e9rica \u00e9 fornecida por S=4\u03c0R2.<\/b><\/span><\/span><\/span><\/p>\n

08- Falsa\u00a0 —\u00a0 veja gr\u00e1fico acima\u00a0 —\u00a0 ele \u00e9 constante e vale V=KQ\/R.<\/b><\/span><\/span><\/span><\/p>\n

16. Correta\u00a0 —\u00a0 todos os pontos internos e da superf\u00edcie possuem o mesmo potencial de valor V=KQ\/R.<\/b><\/span><\/span><\/span><\/p>\n

Corretas: 01, 04 e 16\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0Soma=21<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

39-<\/b><\/span><\/span><\/span> 01. Correta\u00a0 —\u00a0 observe o campo el\u00e9trico uniforme da figura abaixo onde as linhas de for\u00e7a e<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

consequentemente o campo el\u00e9trico se afasta a placa eletrizada com cargas positivas onde o potencial el\u00e9trico \u00e9 maior\u00a0 —\u00a0 uma carga positiva a\u00ed colocada se af\u00e3s da placa positiva (\u00e9 repelida) e se aproxima da placa negativa (\u00e9 atra\u00edda)\u00a0 —\u00a0 se deslocando de A para B ou seja, para pontos de menor potencial el\u00e9trico.<\/b><\/span><\/span><\/span><\/p>\n

02. Falsa\u00a0 —\u00a0 observe na figura abaixo que a carga negativa se desloca para a esquerda, atra\u00edda pela placa positiva e<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

repelida pela negativa, ou seja, se desloca em sentido contr\u00e1rio ao do campo el\u00e9trico.<\/b><\/span><\/span><\/span><\/p>\n

04. Correta\u00a0 —\u00a0 \u00a0Define-se superf\u00edcie equipotencial de um campo el\u00e9trico a qualquer superf\u00edcie em cujos pontos o potencial el\u00e9trico \u00e9 constante.<\/b><\/span><\/span><\/span><\/p>\n

Estas superf\u00edcies t\u00eam duas propriedades importantes:
\n1<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0– A for\u00e7a el\u00e9trica durante o deslocamento de uma carga el\u00e9trica puntiforme sobre uma superf\u00edcie equipotencial \u00e9 nula.<\/b><\/span><\/span><\/span><\/p>\n

2a\u00a0– As superf\u00edcies equipotenciais s\u00e3o perpendiculares \u00e0s linhas de for\u00e7a ou linhas de campo el\u00e9trico e, conseq\u00fcentemente, perpendiculares ao vetor campo el\u00e9trico\u00a0\"\".<\/b><\/span><\/span><\/span><\/p>\n

No caso particular do campo de uma carga puntiforme, a simetria sugere que s\u00e3o superf\u00edcies esf\u00e9ricas conc\u00eantricas com a carga e as linhas de for\u00e7a (de campo) s\u00e3o radiais com o centro da carga.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Campo El\u00e9trico Uniforme<\/b><\/span><\/span><\/span><\/p>\n

\u00a0Um campo el\u00e9trico uniforme tem em todos os seus infinitos pontos mesma intensidade, mesma dire\u00e7\u00e3o e mesmo<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0sentido e \u00e9 obtido entre duas placas condutoras id\u00eanticas e paralelas e eletrizadas com cargas de mesmo m\u00f3dulo, mas de sinais contr\u00e1rios.<\/b><\/span><\/span><\/span><\/p>\n

Observe que nesse caso as superf\u00edcies equipotenciais\u00a0 s\u00e3o planas e paralelas entre si.<\/b><\/span><\/span><\/span><\/p>\n

08. Correta\u00a0 —\u00a0 se existe campo el\u00e9trico tem que existir potencial el\u00e9trico.<\/b><\/span><\/span><\/span><\/p>\n

16. Correta\u00a0 —\u00a0 \u00a0o trabalho de qualquer for\u00e7a conservativa n\u00e3o depende da trajet\u00f3ria, mas apenas das posi\u00e7\u00f5es inicial e final da mesma.<\/b><\/span><\/span><\/span><\/p>\n

Corretas: 01, 04, 08 e16\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>Soma=29<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

40-<\/b><\/span><\/span><\/span> Blindagem eletrost\u00e1tica \u2013 Se, no interior de um condutor oco em equil\u00edbrio eletrost\u00e1tico o campo el\u00e9trico\u00a0\"\"\u00e9 nulo, qualquer aparelho el\u00e9trico e eletr\u00f4nico, quando colocado em seu interior ficar\u00e1 protegido de influ\u00eancias perturbadoras externas\u00a0 —\u00a0 a blindagem eletrost\u00e1tica (gaiola de Faraday) tamb\u00e9m \u00e9 utilizada nos carros e avi\u00f5es, oferecendo prote\u00e7\u00e3o contra descargas<\/b><\/span><\/span><\/span><\/p>\n

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

\u00a0el\u00e9tricas. Constru\u00e7\u00f5es tamb\u00e9m s\u00e3o feitas utilizando blindagem eletrost\u00e1tica, a fim de proteger seus equipamentos el\u00e9tricos e eletr\u00f4nicos.<\/b><\/span><\/span><\/span><\/p>\n

R- B<\/b><\/span><\/span><\/span><\/p>\n

41-<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

a) Cargas negativas (\u00edons negativos \u2013 Cl<\/b><\/span><\/span><\/span>–<\/b><\/span><\/span><\/sup><\/span>) deslocam-se para pontos de maior potencial, do interior para o exterior da c\u00e9lula\u00a0 —\u00a0 cargas positivas\u00a0 (\u00edons positivos \u2013 Ca<\/b><\/span><\/span><\/span>2+<\/b><\/span><\/span><\/sup><\/span>) deslocam-se para pontos de menor potencial, do exterior para o interior da c\u00e9lula.<\/b><\/span><\/span><\/span><\/p>\n

b) No interior da membrana (interior do capacitor), pelo gr\u00e1fico a ddp U=(64.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0\u2013 0)=64.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>m\u00a0 —\u00a0 U=E.d\u00a0 — 64.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>=E.8.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0<\/b><\/span><\/span><\/span>E=8,0.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>V\/m ou N\/C<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

c) For\u00e7a el\u00e9trica sobre os \u00edons Cl<\/b><\/span><\/span><\/span>–<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 F<\/b><\/span><\/span><\/span>Cl<\/b><\/span><\/span><\/sub><\/span>=|q|.E=1.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>.8.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0F<\/b><\/span><\/span><\/span>Cl<\/b><\/span><\/span><\/sub><\/span>=1,28.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>N\u00a0<\/b><\/span><\/span><\/span>\u00a0—\u00a0 for\u00e7a el\u00e9trica sobre os \u00edons Ca<\/b><\/span><\/span><\/span>2+<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 F<\/b><\/span><\/span><\/span>Ca<\/b><\/span><\/span><\/sub><\/span>=|q|.E=2.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>.8.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>F<\/b><\/span><\/span><\/span>Cl<\/b><\/span><\/span><\/sub><\/span>=2,56.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>N.<\/b><\/span><\/span><\/span><\/p>\n

d<\/b><\/span><\/span><\/span>)\u00a0<\/b><\/span><\/span><\/span>Pela defini\u00e7\u00e3o de capacit\u00e2ncia, sendo Q a carga el\u00e9trica na superf\u00edcie externa da membrana\u00a0 —\u00a0 C=Q\/U\u00a0 —\u00a0 12.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>=Q\/64.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0<\/b><\/span><\/span><\/span>Q=7,68.10<\/b><\/span><\/span><\/span>-13<\/b><\/span><\/span><\/sup><\/span>C.<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Voltar para os exerc\u00edcios<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Resolu\u00e7\u00e3o comentada das quest\u00f5es de vestibulares sobre o conte\u00fado Condutor em equil\u00edbrio eletrost\u00e1tico \u2013 Blindagem eletrost\u00e1tica   01- R- D\u00a0 —\u00a0 veja teoria 02- R- B 03-\u00a0A descarga el\u00e9trica ocorrida ir\u00e1 eletrizar o avi\u00e3o\u00a0 —\u00a0 por\u00e9m, como sua fuselagem \u00e9 met\u00e1lica (bom condutor), essas cargas ir\u00e3o se distribuir na superf\u00edcie externa, n\u00e3o causando danos aos passageiros. A fuselagem atua como<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1664,"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-1670","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1670","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=1670"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1670\/revisions"}],"predecessor-version":[{"id":10613,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1670\/revisions\/10613"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1664"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=1670"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}