{"id":3318,"date":"2017-10-01T14:15:49","date_gmt":"2017-10-01T14:15:49","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=3318"},"modified":"2024-09-04T14:05:58","modified_gmt":"2024-09-04T14:05:58","slug":"resolucao-eletrostatica-2017-2016-2015","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/vestibulares-recentes\/eletricidade\/eletrostatica-2017-2016-2015\/resolucao-eletrostatica-2017-2016-2015\/","title":{"rendered":"Resolu\u00e7\u00e3o Eletrost\u00e1tica – 2017 – 2016 – 2015"},"content":{"rendered":"

Resolu\u00e7\u00e3o Comentada \u2013 2017- 2016 \u2013 2015<\/span><\/span><\/span><\/p>\n

ELETROST\u00c1TICA<\/span><\/span><\/span><\/p>\n

01-<\/span><\/span><\/span> Coment\u00e1rio 1. Falso\u00a0<\/b><\/span><\/span>\u2014 <\/b><\/span><\/span>todas as part\u00edculas (mat\u00e9ria) possuem massa.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Coment\u00e1rios 2 e 3<\/b><\/span><\/span> – <\/b><\/span><\/span>\u00a0<\/b><\/span>Corretos.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

02- <\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

03- <\/span><\/span><\/span><\/span><\/span><\/p>\n

Em uma eletriza\u00e7\u00e3o por contato a carga \u00e9\u00a0<\/b><\/span><\/span>distribu\u00edda entre os condutores<\/b><\/span><\/span>, portanto ap\u00f3s o contato<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

ambos os condutores ficam carregados<\/b><\/span><\/span>. Nesse caso,\u00a0<\/b><\/span><\/span>a carga <\/b><\/span><\/span>depende das dimens\u00f5es do condutor, <\/b><\/span><\/span>portanto elas\u00a0<\/b><\/span><\/span>n\u00e3o ter\u00e3o a mesma carga final<\/b><\/span><\/span>, sendo a <\/b><\/span><\/span>alternativa certa a B<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

04- <\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

05- <\/span><\/span><\/span><\/span><\/span><\/p>\n

a)\u00a0<\/b><\/span><\/span>Incorreta\u00a0\"\"<\/b><\/span><\/span>\u00a0a\u00a0<\/b><\/span><\/span>quantidade de el\u00e9trons livres\u00a0<\/b><\/span><\/span>no interior de um corpo\u00a0<\/b><\/span><\/span>n\u00e3o tem rela\u00e7\u00e3o nenhuma com o fato de ele ser isolante (grande dificuldade de serem eletrizados).\u00a0<\/b><\/span><\/span>No\u00a0<\/b><\/span><\/span>isolante,<\/b><\/span><\/span>\u00a0os\u00a0<\/b><\/span><\/span>el\u00e9trons livres, independente de sua quantidade tem grande dificuldade de se movimentarem.<\/b><\/span><\/span><\/span><\/span><\/p>\n

b)\u00a0<\/b><\/span><\/span>Incorreta<\/b><\/span><\/span>\u00a0\"\"\u00a0os corpos condutores\u00a0<\/b><\/span><\/span>se\u00a0<\/b><\/span><\/span>eletrizam com facilidade\u00a0<\/b><\/span><\/span>mas isso\u00a0<\/b><\/span><\/span>n\u00e3o tem rela\u00e7\u00e3o\u00a0<\/b><\/span><\/span>com a\u00a0<\/b><\/span><\/span>quantidade de el\u00e9trons livres.\u00a0<\/b><\/span><\/span>No\u00a0<\/b><\/span><\/span>condutor,<\/b><\/span><\/span>\u00a0os\u00a0<\/b><\/span><\/span>el\u00e9trons livres, independente de sua quantidade tem grande facilidade de se movimentarem.<\/b><\/span><\/span><\/span><\/span><\/p>\n

c)\u00a0<\/b><\/span><\/span>Correta<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0A\u00a0<\/b><\/span><\/span>for\u00e7a el\u00e9trica entre dois corpos eletrizados\u00a0<\/b><\/span><\/span>pode ser\u00a0<\/b><\/span><\/span>atrativa ou repulsiva, dependendo apenas da carga el\u00e9trica dos corpos.\u00a0\u00a0<\/b><\/span><\/span>Se as\u00a0<\/b><\/span><\/span>cargas el\u00e9tricas tiverem mesmo sinal\u00a0<\/b><\/span><\/span>a for\u00e7a entre elas\u00a0<\/b><\/span><\/span>ser\u00e1 de repuls\u00e3o\u00a0<\/b><\/span><\/span>e, se tiverem <\/b><\/span><\/span>sinais opostos, de atra\u00e7\u00e3o.
\nd)\u00a0<\/b><\/span><\/span>Correta\u00a0\"\"\u00a0<\/b><\/span><\/span>A\u00a0<\/b><\/span><\/span>passagem da corrente el\u00e9trica\u00a0<\/b><\/span><\/span>por um\u00a0<\/b><\/span><\/span>fio condutor\u00a0<\/b><\/span><\/span>produz um<\/b><\/span><\/span>campo magn\u00e9tico em volta desse fio<\/b><\/span><\/span>, que pode ser verificado pela\u00a0<\/b><\/span><\/span>presen\u00e7a de uma b\u00fassola.\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

e)\u00a0<\/b><\/span><\/span>Incorreta<\/b><\/span><\/span>\u00a0\"\"\u00a0<\/b><\/span><\/span>Os\u00a0<\/b><\/span><\/span>motores el\u00e9tricos funcionam\u00a0<\/b><\/span><\/span>devido ao aparecimento de\u00a0<\/b><\/span><\/span>for\u00e7as de origem magn\u00e9tica<\/b><\/span><\/span>\u00a0cujo movimento deve-se \u00e0\u00a0<\/b><\/span><\/span>passagem de corrente el\u00e9trica nas espiras no interior desse motor.<\/b><\/span><\/span><\/span><\/span><\/p>\n

R \u2013 quest\u00e3o anulada<\/b><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span>existe mais de uma op\u00e7\u00e3o incorreta.<\/b><\/span><\/span><\/span><\/span><\/p>\n

06- <\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Como, pelo\u00a0<\/b><\/span><\/span>enunciado, X estava eletrizada com carga de 5,0.10<\/b><\/span><\/span>-12<\/b><\/span><\/sup><\/span>\u00a0\u00a0C<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>ela transferiu<\/b><\/span><\/span>toda sua carga\u00a0<\/b><\/span><\/span>para Y,<\/b><\/span><\/span>\u00a0ficando\u00a0<\/b><\/span><\/span>X neutra (carga zero).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Acontece que\u00a0<\/b><\/span><\/span>todo corpo ligado \u00e0 Terra fica totalmente descarregado <\/b><\/span><\/span>transferindo integralmente\u00a0<\/b><\/span><\/span>toda sua carga (5,0.10<\/b><\/span><\/span>-12<\/b><\/span><\/sup><\/span>\u00a0C) para a Terra.<\/b><\/span><\/span>\u00a0Assim\u00a0<\/b><\/span><\/span>Y tamb\u00e9m ficar\u00e1 neutro com carga zero.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Portanto, no\u00a0<\/b><\/span><\/span>final desse processo,<\/b><\/span><\/span>\u00a0as\u00a0<\/b><\/span><\/span>cargas el\u00e9tricas totais dos objetos X e Y ser\u00e3o, respectivamente, zero e zero.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

07- <\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

08- <\/span><\/span><\/span><\/span><\/span><\/p>\n

Lei de Coulomb ou For\u00e7a el\u00e9trica<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"A\u00a0<\/b><\/span><\/span>express\u00e3o matem\u00e1tica<\/b><\/span><\/span>\u00a0acima \u00e9 denominada\u00a0<\/b><\/span><\/span>lei de Coulomb<\/b><\/span><\/span>\u00a0e de enunciado:<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"Esta constante K<\/b><\/span><\/span>\u00a0<\/b><\/span>\u00e9\u00a0<\/b><\/span><\/span>dependente<\/b><\/span><\/span>\u00a0do\u00a0<\/b><\/span><\/span>meio onde est\u00e3o as cargas (denominada constante eletrost\u00e1tica<\/b><\/span><\/span>\u00a0<\/b><\/span>do meio ou constante diel\u00e9trica)<\/b><\/span><\/span>\u00a0e, no\u00a0<\/b><\/span><\/span>sistema internacional de unidades (SI) e, no v\u00e1cuo<\/b><\/span><\/span>\u00a0e\u00a0<\/b><\/span><\/span>aproximadamente no ar, tem valor<\/b><\/span><\/span>\u00a0\"\"\u00a0<\/b><\/span><\/span>K = 1\/4\u03c0\u03b5o\u00a0\u2248 8,9876.109\u00a0Nm2\/C2\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>costuma ser arredondado para\u00a0K = 9.109\u00a0Nm2\/C2.<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Pelo enunciado<\/b><\/span><\/span>, QA\u00a0+ QB\u00a0= 20 nC\u00a0<\/b><\/span><\/span>\uf0de<\/b><\/span><\/span><\/span>\u00a0QA\u00a0= 20.10-9<\/b><\/span><\/span>\u00a0<\/b><\/span>– QB\u00a0e\u00a0<\/b><\/span><\/span>aplicando<\/b><\/span><\/span>\u00a0a Lei de Coulomb,\u00a0<\/b><\/span><\/span>temos:<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Resolvendo a equa\u00e7\u00e3o do segundo grau:<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

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

09- <\/span><\/span><\/span>Vamos analisar as cargas:<\/b><\/span><\/span><\/span><\/span><\/p>\n

A carga\u00a0<\/b><\/span><\/span>-Q<\/b><\/span><\/span>\u00a0vai exercer uma\u00a0<\/b><\/span><\/span>for\u00e7a de repuls\u00e3o\u00a0<\/b><\/span><\/span>(negativo com negativo), enquanto que a carga\u00a0<\/b><\/span><\/span>+Q<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

exerce uma for\u00e7a de\u00a0<\/b><\/span><\/span>atra\u00e7\u00e3o<\/b><\/span><\/span>\u00a0(positivo e negativo), assim a \u00fanica resposta poss\u00edvel \u00e9 a alternativa\u00a0<\/b><\/span><\/span>a<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

10- <\/span><\/span><\/span>A\u00a0<\/b><\/span><\/span>\u00fanica errada\u00a0<\/b><\/span><\/span>\u00e9 a alternativa\u00a0<\/b><\/span><\/span>C<\/b><\/span><\/span>, pois, pela\u00a0<\/b><\/span><\/span>lei de Coulomb\u00a0<\/b><\/span><\/span>a\u00a0<\/b><\/span><\/span>for\u00e7a de repuls\u00e3o\u00a0<\/b><\/span><\/span>entre as cargas \u00e9\u00a0<\/b><\/span><\/span>fornecida<\/b><\/span><\/span>\u00a0por\u00a0<\/b><\/span><\/span>F = kq1.q2\/d<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>\u00a0(F \u00e9 diretamente proporcional ao m\u00f3dulo das cargas e inversamente proporcional ao quadrado da dist\u00e2ncia entre elas).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Assim, quando voc\u00ea\u00a0<\/b><\/span><\/span>triplica o valor de uma das cargas F fica 3 vezes maior\u00a0<\/b><\/span><\/span>e, quando voc\u00ea\u00a0<\/b><\/span><\/span>triplica a dist\u00e2ncia entre as cargas F fica 32\u00a0= 9 vezes menor.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Assim,\u00a0<\/b><\/span><\/span>F ficar\u00e1<\/b><\/span><\/span>\u00a0\"\"\u00a0=\u00a0\"\"<\/b><\/span><\/span>\u00a0(3 vezes menor) e n\u00e3o inalterada.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

11- <\/span><\/span><\/span>Sobre o\u00a0<\/b><\/span><\/span>feixe de el\u00e9trons (carga negativa),<\/b><\/span><\/span>\u00a0a\u00a0<\/b><\/span><\/span>for\u00e7a resultante deve<\/b><\/span><\/span>\u00a0ter a\u00a0<\/b><\/span><\/span>dire\u00e7\u00e3o e o sentido de\u00a0\"\"<\/b><\/span><\/span>(vertical e para cima),\u00a0<\/b><\/span><\/span>para que<\/b><\/span><\/span>\u00a0o\u00a0<\/b><\/span><\/span>movimento do feixe seja retil\u00edneo e acelerado dentro da regi\u00e3o plana delimitada pelo quadrado. As cargas de cada esfera devem ter o mesmo m\u00f3dulo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Para que a\u00a0<\/b><\/span><\/span>trajet\u00f3ria seja retil\u00ednea, vertical e para cima<\/b><\/span><\/span>, a\u00a0<\/b><\/span><\/span>dire\u00e7\u00e3o da for\u00e7a el\u00e9trica na horizontal deve ser nula, de modo que ele n\u00e3o se mova nessa dire\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"R \u2013 C<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

12- <\/span><\/span><\/span>Pelo enunciado<\/b><\/span><\/span>, como a esfera\u00a0<\/b><\/span><\/span>desce<\/b><\/span><\/span>\u00a0no interior da c\u00e2mara com<\/b><\/span><\/span>velocidade constante\u00a0<\/b><\/span><\/span>ent\u00e3o ela est\u00e1 em\u00a0<\/b><\/span><\/span>equil\u00edbrio din\u00e2mico<\/b><\/span><\/span>\u00a0e a\u00a0<\/b><\/span><\/span>for\u00e7a resultante<\/b><\/span><\/span>\u00a0sobre ela deve ser\u00a0<\/b><\/span><\/span>nula.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Sendo a\u00a0<\/b><\/span><\/span>for\u00e7a peso vertical e para baixo<\/b><\/span><\/span>, a\u00a0<\/b><\/span><\/span>for\u00e7a el\u00e9trica<\/b><\/span><\/span>\u00a0sobre a esfera,<\/b><\/span><\/span>para anular o peso<\/b><\/span><\/span>, deve ter\u00a0<\/b><\/span><\/span>dire\u00e7\u00e3o vertical e sentido para cima.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Se,\u00a0<\/b><\/span><\/span>pelo enunciado, o\u00a0<\/b><\/span><\/span>campo el\u00e9trico<\/b><\/span><\/span>\u00a0uniforme tem a mesma dire\u00e7\u00e3o e sentido da acelera\u00e7\u00e3o local da<\/b><\/span><\/span>\u00a0<\/b><\/span>gravidade\u00a0<\/b><\/span><\/span>(vertical e para baixo),<\/b><\/span><\/span>\u00a0a\u00a0<\/b><\/span><\/span>esfera <\/b><\/span><\/span>deve estar eletrizada com\u00a0<\/b><\/span><\/span>carga negativa\u00a0<\/b><\/span><\/span>(excesso de<\/b><\/span><\/span>\u00a0<\/b><\/span>el\u00e9trons<\/b><\/span><\/span>)<\/b><\/span><\/span>, pois, para <\/b><\/span><\/span>cargas negativas a for\u00e7a el\u00e9trica e o campo el\u00e9trico<\/b><\/span><\/span>\u00a0t\u00eam mesma dire\u00e7\u00e3o<\/b><\/span><\/span>(vertical)<\/b><\/span><\/span>\u00a0e\u00a0<\/b><\/span><\/span>sentido contr\u00e1rio<\/b><\/span><\/span>\u00a0<\/b><\/span>(campo para baixo e for\u00e7a para cima).<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

13- <\/span><\/span><\/span>Lembre-se que\u00a0<\/b><\/span><\/span>cargas el\u00e9tricas positivas criam no ponto P campos el\u00e9tricos de afastamento e negativas, de aproxima\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Se a\u00a0<\/b><\/span><\/span>intensidade do campo el\u00e9trico criado por Q1\u00a0em P tem m\u00f3dulo E\u00a0<\/b><\/span><\/span>as\u00a0<\/b><\/span><\/span>outras cargas<\/b><\/span><\/span>, de\u00a0<\/b><\/span><\/span>mesmo m\u00f3dulo,<\/b><\/span><\/span>\u00a0tamb\u00e9m\u00a0<\/b><\/span><\/span>originar\u00e3o em P campos de intensidades E<\/b><\/span><\/span>, pois E\u00a0<\/b><\/span><\/span>=\u00a0\"\"<\/b><\/span><\/span>, com\u00a0<\/b><\/span><\/span>k,\u2502Q\u2502e d2\u00a0constantes.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Veja nas\u00a0<\/b><\/span><\/span>figuras a representa\u00e7\u00e3o da dire\u00e7\u00e3o e sentido dos campos criados em P<\/b><\/span><\/span>por\u00a0<\/b><\/span><\/span>cada carga\u00a0<\/b><\/span><\/span>(positiva, de afastamento e negativa, de aproxima\u00e7\u00e3o), e a<\/b><\/span><\/span>sequ\u00eancia do c\u00e1lculo da intensidade\u00a0<\/b><\/span><\/span>do campo el\u00e9trico resultante ER.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Aplicando\u00a0<\/b><\/span><\/span>Pit\u00e1goras na terceira figura\u00a0<\/b><\/span><\/span>(tri\u00e2ngulo ret\u00e2ngulo)\u00a0\"\"\u00a0<\/b><\/span><\/span>ER<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>\u00a0= (2E)<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>\u00a0+ (2E)<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>\u00a0<\/b><\/span>= 2.(2E)<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span><\/span><\/p>\n

ER\u00a0=2.E.\"\"<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

14- <\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

15-<\/span><\/span><\/span><\/span><\/span><\/p>\n


\n<\/b><\/span><\/span>Potencial el\u00e9trico V\"\"<\/b><\/span><\/span><\/span><\/span><\/p>\n

Sendo o\u00a0<\/b><\/span><\/span>potencial el\u00e9trico uma grandeza escalar,<\/b><\/span><\/span>\u00a0o\u00a0<\/b><\/span><\/span>potencial el\u00e9trico no ponto C (VC)\u00a0<\/b><\/span><\/span>\u00e9\u00a0<\/b><\/span><\/span>a soma\u00a0<\/b><\/span><\/span>dos\u00a0<\/b><\/span><\/span>potenciais de cada carga\u00a0<\/b><\/span><\/span>(princ\u00edpio da superposi\u00e7\u00e3o)\u00a0<\/b><\/span><\/span>nesse ponto equidistante r de cada carga.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"
\n<\/b><\/span><\/span>Campo el\u00e9trico gerado num ponto P por v\u00e1rias cargas puntiformes<\/b><\/span><\/span><\/span><\/span><\/p>\n

Num\u00a0<\/b><\/span><\/span>dado ponto P\u00a0<\/b><\/span><\/span>do espa\u00e7o o\u00a0<\/b><\/span><\/span>vetor campo el\u00e9trico resultante<\/b><\/span><\/span>, devido \u00e0\u00a0<\/b><\/span><\/span>a\u00e7\u00e3o<\/b><\/span><\/span>\u00a0de\u00a0<\/b><\/span><\/span>v\u00e1rias cargas,<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

corresponde \u00e0\u00a0<\/b><\/span><\/span>soma vetorial\u00a0dos campos produzidos por cada uma dessas cargas individualmente.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

16- <\/span><\/span><\/span><\/span><\/span><\/p>\n

Campo el\u00e9trico gerado por uma carga pontual Q<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"\u00a0<\/span>Uma\u00a0<\/b><\/span><\/span>carga puntiforme (Q)<\/b><\/span><\/span>\u00a0geradora de campo\u00a0<\/b><\/span><\/span>provoca num ponto P<\/b><\/span><\/span>, distante\u00a0<\/b><\/span><\/span>d\u00a0<\/b><\/span><\/span>da carga, um\u00a0<\/b><\/span><\/span>vetor<\/b><\/span><\/span>\u00a0<\/b><\/span>campo el\u00e9trico\u00a0\"\"\u00a0que faz surgir sobre uma carga de prova q a\u00ed colocada uma for\u00e7a el\u00e9trica\u00a0\"\"\u00a0de intensidade F=KQq\/d<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>, que substitu\u00edda na equa\u00e7\u00e3o E=F\/q fornece:<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

\u00a0<\/span>Observe\u00a0<\/b><\/span><\/span>atentamente as figuras abaixo<\/b><\/span><\/span>\u00a0onde a carga geradora\u00a0<\/b><\/span><\/span>Q > 0<\/b><\/span><\/span>provoca em\u00a0<\/b><\/span><\/span>q1\u00a0< 0<\/b><\/span><\/span>\u00a0localizado em M uma for\u00e7a de atra\u00e7\u00e3o\u00a0\"\"\u00a0e, como\u00a0<\/b><\/span><\/span>q1\u00a0\u00e9 negativa, campo e for\u00e7a tem mesma dire\u00e7\u00e3o e sentidos opostos, estando\"\"\u00a0em M se\u00a0<\/b><\/span><\/span>afastando<\/b><\/span><\/span>\u00a0de Q > 0.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Verifique agora que a\u00a0<\/b><\/span><\/span>carga geradora Q > 0 provoca em q2\u00a0> 0<\/b><\/span><\/span>\u00a0localizado em\u00a0<\/b><\/span><\/span>N\u00a0<\/b><\/span><\/span>uma for\u00e7a de
\n<\/b><\/span><\/span>repuls\u00e3o\u00a0\"\"<\/b><\/span><\/span>\u00a0e, como\u00a0<\/b><\/span><\/span>q2\u00a0\u00e9 positiva,<\/b><\/span><\/span>\u00a0campo e for\u00e7a t\u00eam\u00a0<\/b><\/span><\/span>mesma dire\u00e7\u00e3o e mesmo sentido, estando<\/b><\/span><\/span>\u00a0\"\"\u00a0<\/b><\/span><\/span>em N se afastando de Q > 0<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Generalizando:\u00a0<\/b><\/span><\/span>em qualquer ponto do\u00a0campo gerado por Q > 0\u00a0colocando-se cargas de prova q positivas ou negativas, o campo gerado\u00a0ser\u00e1 sempre de afastamento.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Analogamente, se a\u00a0carga geradora fosse negativa Q < 0, em\u00a0todos os pontos o campo el\u00e9trico gerado seria de aproxima\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Como o\u00a0<\/b><\/span><\/span>el\u00e9tron (carga de prova negativa)<\/b><\/span><\/span>\u00a0se desloca para a\u00a0<\/b><\/span><\/span>direita a for\u00e7a sobre ele tamb\u00e9m \u00e9 para a direita e o campo el\u00e9trico \u00e9 para a esquerda.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

17- <\/span><\/span><\/span>
\nPotencial el\u00e9trico V\"\"<\/b><\/span><\/span><\/span><\/span><\/p>\n

Sendo o\u00a0<\/b><\/span><\/span>potencial el\u00e9trico uma grandeza escalar,<\/b><\/span><\/span>\u00a0o\u00a0<\/b><\/span><\/span>potencial el\u00e9trico no ponto C (VC)\u00a0<\/b><\/span><\/span>\u00e9\u00a0<\/b><\/span><\/span>a soma\u00a0<\/b><\/span><\/span>dos\u00a0<\/b><\/span><\/span>potenciais de cada carga\u00a0<\/b><\/span><\/span>(princ\u00edpio da superposi\u00e7\u00e3o)\u00a0<\/b><\/span><\/span>nesse ponto equidistante r de cada carga.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"
\n<\/b><\/span><\/span>Campo el\u00e9trico gerado num ponto P por v\u00e1rias cargas puntiformes<\/b><\/span><\/span><\/span><\/span><\/p>\n

Num\u00a0<\/b><\/span><\/span>dado ponto P\u00a0<\/b><\/span><\/span>do espa\u00e7o o\u00a0<\/b><\/span><\/span>vetor campo el\u00e9trico resultante<\/b><\/span><\/span>, devido \u00e0\u00a0<\/b><\/span><\/span>a\u00e7\u00e3o<\/b><\/span><\/span>\u00a0de\u00a0<\/b><\/span><\/span>v\u00e1rias cargas,<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

corresponde \u00e0\u00a0<\/b><\/span><\/span>soma vetorial\u00a0dos campos produzidos por cada uma dessas cargas individualmente.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

18- <\/span><\/span><\/span>a)<\/b><\/span><\/span>\u00a0os\u00a0<\/b><\/span><\/span>m\u00f3dulos EA, EB\u00a0e EC<\/b><\/span><\/span>\u00a0<\/b><\/span>do\u00a0<\/b><\/span><\/span>campo el\u00e9trico<\/b><\/span><\/span>\u00a0nos pontos\u00a0<\/b><\/span><\/span>A, B e C, respectivamente;<\/b><\/span><\/span><\/span><\/span><\/p>\n

S\u00e3o fornecidos<\/b><\/span><\/span>\u00a0a\u00a0<\/b><\/span><\/span>diferen\u00e7a de potencial entre as placas<\/b><\/span><\/span>\u00a0V = 300V e a<\/b><\/span><\/span>dist\u00e2ncia entre as placas<\/b><\/span><\/span>\u00a0d=5 mm = 5.10<\/b><\/span><\/span>-3<\/b><\/span><\/sup><\/span>\u00a0m.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

20- <\/span><\/span><\/span>
\n\"\"<\/b><\/span><\/span><\/span><\/span><\/p>\n

W = q.(VA\u00a0\u2013 VB)<\/b><\/span><\/span>\u00a0= 1,2.10<\/b><\/span><\/span>-6<\/b><\/span><\/sup><\/span>.(10 \u2013 3)\u00a0<\/b><\/span><\/span>= 8,4.10<\/b><\/span><\/span>-6<\/b><\/span><\/sup><\/span>\u00a0J = 8,4\u00a0\"\"J.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

21- <\/span><\/span><\/span><\/span><\/span><\/p>\n

VA\u00a0=\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span>= 9.109.7.10-6\/5.10-2<\/b><\/span><\/span>\u00a0<\/b><\/span>= 12,6.105\u00a0V<\/b><\/span><\/span><\/span><\/span><\/p>\n

VB\u00a0=\u00a0\"\"<\/b><\/span><\/span>\u00a0<\/b><\/span>= 9.109.7.10-6\/59.10-2<\/b><\/span><\/span>\u00a0<\/b><\/span>= 7.105\u00a0V<\/b><\/span><\/span><\/span><\/span><\/p>\n

UAB\u00a0= (VA\u00a0\u2013 VB)\u00a0<\/b><\/span><\/span>= (12,6 -7).105<\/b><\/span><\/span>\u00a0<\/b><\/span>= 5,6.105\u00a0V.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

22- <\/span><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O\u00a0<\/b><\/span><\/span>trabalho entre A e C n\u00e3o depende da trajet\u00f3ria\u00a0<\/b><\/span><\/span>(as linhas verticais s\u00e3o superf\u00edcies equipotenciais) mas,\u00a0<\/b><\/span><\/span>WAC\u00a0= q.U = q.E.d<\/b><\/span><\/span>\u00a0= 0,1.10<\/b><\/span><\/span>-6<\/b><\/span><\/sup><\/span>.5.10<\/b><\/span><\/span>2<\/b><\/span><\/sup><\/span>.10.10<\/b><\/span><\/span>-2<\/b><\/span><\/sup><\/span>\u00a0<\/b><\/span>= 5.10<\/b><\/span><\/span>-5<\/b><\/span><\/sup><\/span>\u00a0J.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

23- <\/span><\/span><\/span>Veja o<\/b><\/span><\/span>\u00a0formul\u00e1rio abaixo:<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"No\u00a0<\/b><\/span><\/span>trabalho das for\u00e7as conservativas<\/b><\/span><\/span>\u00a0(for\u00e7a el\u00e9trica) temos que\u00a0\"\"
\n\"\", ou seja, o\u00a0<\/b><\/span><\/span>trabalho realizado\u00a0<\/b><\/span><\/span>pela for\u00e7a el\u00e9trica para a carga de\u00a0<\/b><\/span><\/span>q = 400 \u03bcC= 400.10<\/b><\/span><\/span><\/span><\/span><\/p>\n

-6<\/b><\/span><\/sup><\/span>\u00a0C,\u00a0<\/b><\/span><\/span>para se\u00a0<\/b><\/span><\/span>deslocar de A (VA\u00a0= 100 V) at\u00e9 B (VB\u00a0= 20 V)\u00a0<\/b><\/span><\/span>pode ser\u00a0<\/b><\/span><\/span>calculado\u00a0<\/b><\/span><\/span>pela\u00a0<\/b><\/span><\/span>diferen\u00e7a entre a Energia potencial inicial e Energia potencial final.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

24- <\/span><\/span><\/span>Mesmas cargas el\u00e9tricas\u00a0<\/b><\/span><\/span>(mesmo sinal) se repelem.<\/b><\/span><\/span>\u00a0Para\u00a0<\/b><\/span><\/span>aproxim\u00e1-las<\/b><\/span><\/span>, voc\u00ea deve exercer\u00a0<\/b><\/span><\/span>for\u00e7a<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

contra<\/b><\/span><\/span>\u00a0<\/b><\/span>o campo el\u00e9trico<\/b><\/span><\/span>. Essa for\u00e7a\u00a0<\/b><\/span><\/span>provoca em aumento da energia potencial el\u00e9trica do sistema das duas cargas.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

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

Resolu\u00e7\u00e3o Comentada \u2013 2017- 2016 \u2013 2015 ELETROST\u00c1TICA 01- Coment\u00e1rio 1. Falso\u00a0\u2014 todas as part\u00edculas (mat\u00e9ria) possuem massa. Coment\u00e1rios 2 e 3 – \u00a0Corretos. R- A 02- 03- Em uma eletriza\u00e7\u00e3o por contato a carga \u00e9\u00a0distribu\u00edda entre os condutores, portanto ap\u00f3s o contato ambos os condutores ficam carregados. Nesse caso,\u00a0a carga depende das dimens\u00f5es do condutor, portanto elas\u00a0n\u00e3o ter\u00e3o a<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3316,"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-3318","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3318","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=3318"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3318\/revisions"}],"predecessor-version":[{"id":3321,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3318\/revisions\/3321"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3316"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=3318"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}