{"id":1721,"date":"2015-12-31T03:06:28","date_gmt":"2015-12-31T03:06:28","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=1721"},"modified":"2024-06-24T13:30:28","modified_gmt":"2024-06-24T13:30:28","slug":"resistores-primeira-lei-de-ohm","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/eletricidade\/eletrodinamica\/resistores-primeira-lei-de-ohm\/","title":{"rendered":"Resistores \u2013 Primeira lei de Ohm"},"content":{"rendered":"

Resistores \u2013 Primeira lei de Ohm \u2013 Pot\u00eancia el\u00e9trica de um resistor<\/b><\/span><\/span><\/span><\/p>\n

Efeito Joule<\/b><\/span><\/span><\/span><\/p>\n

\"\"\u00a0<\/span>E<\/b><\/span><\/span><\/span>feito Joule<\/b><\/span><\/span><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0 num <\/b><\/span><\/span><\/span>condutor met\u00e1lico<\/b><\/span><\/span><\/span>, os <\/b><\/span><\/span><\/span>el\u00e9trons livres da corrente el\u00e9trica,<\/b><\/span><\/span><\/span> <\/b>durante suas<\/b><\/span><\/span><\/span> <\/b>movimenta\u00e7\u00f5es,<\/b><\/span><\/span><\/span> sofrem continuamente <\/b><\/span><\/span><\/span>colis\u00f5es<\/b><\/span><\/span><\/span> com os <\/b><\/span><\/span><\/span>\u00e1tomos da rede cristalina desse condutor,<\/b><\/span><\/span><\/span> transferindo a eles\u00a0 <\/b><\/span><\/span><\/span>parte <\/b><\/span><\/span><\/span>de sua <\/b><\/span><\/span><\/span>energia cin\u00e9tica e, como resultado, os \u00e1tomos do condutor,<\/b><\/span><\/span><\/span> como um todo, passam a <\/b><\/span><\/span><\/span>vibrar com uma energia maior.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Esse <\/b><\/span><\/span><\/span>aumento do \u201cn\u00edvel de vibra\u00e7\u00e3o\u201d dos \u00e1tomos<\/b><\/span><\/span><\/span> do condutor <\/b><\/span><\/span><\/span>provocam um aumento<\/b><\/span><\/span><\/span> de sua <\/b><\/span><\/span><\/span>temperatura,<\/b><\/span><\/span><\/span> fazendo-o <\/b><\/span><\/span><\/span>liberar energia t\u00e9rmica (calor).<\/b><\/span><\/span><\/span> <\/b>Esse fen\u00f4meno \u00e9 denominado efeito Joule.<\/b><\/span><\/span><\/span><\/p>\n

Geradores e receptores<\/b><\/span><\/span><\/span><\/p>\n

\"\"\u00a0\u00a0<\/span>Geradores<\/b><\/span><\/span><\/span> \"\" Nos <\/b><\/span><\/span><\/span>circuitos el\u00e9tricos<\/b><\/span><\/span><\/span> existem, al\u00e9m de outros elementos, os <\/b><\/span><\/span><\/span>geradores cuja fun\u00e7\u00e3o \u00e9 <\/b><\/span><\/span><\/span><\/b>transformar qualquer tipo de energia em energia el\u00e9trica.<\/b><\/span><\/span><\/span>Exemplos: <\/b><\/span><\/span><\/span>pilhas e baterias<\/b><\/span><\/span><\/span>, nas<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

quais ocorrem a <\/b><\/span><\/span><\/span>convers\u00e3o de energia qu\u00edmica em energia el\u00e9trica.<\/b><\/span><\/span><\/span> Nas <\/b><\/span><\/span><\/span>usinas hidrel\u00e9tricas<\/b><\/span><\/span><\/span> ocorre a transforma\u00e7\u00e3o <\/b><\/span><\/span><\/span>de energia mec\u00e2nica das \u00e1guas em movimento em energia el\u00e9trica, atrav\u00e9s de geradores, etc.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\" \u00a0Um <\/b><\/span><\/span><\/span>ohm (1\u2126)<\/b><\/span><\/span><\/span> \u00e9 o <\/b><\/span><\/span><\/span>valor da resist\u00eancia el\u00e9trica <\/b><\/span><\/span><\/span>entre dois pontos P e Q de um <\/b><\/span><\/span><\/span>condutor <\/b><\/span><\/span><\/span>quando, <\/b><\/span><\/span><\/span>sob diferen\u00e7a de potencial de 1 volt (1V<\/b><\/span><\/span><\/span>) \u00e9 percorrido por uma<\/b><\/span><\/span><\/span>corrente el\u00e9trica constante de 1 amp\u00e8re (1A).<\/b><\/span><\/span><\/span><\/p>\n

\"\"\u00a0\u00a0<\/span>Representa\u00e7\u00e3o simb\u00f3lica de um resistor:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Quanto <\/b><\/span><\/span><\/span>maior a inclina\u00e7\u00e3o da reta,<\/b><\/span><\/span><\/span> maior ser\u00e1 o \u00e2ngulo, sendo, portanto<\/b><\/span><\/span><\/span>, maior a resist\u00eancia do condutor (resistor).<\/b><\/span><\/span><\/span><\/p>\n

Pot\u00eancia el\u00e9trica de um condutor resistivo (resistor)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

O que voc\u00ea deve saber, informa\u00e7\u00f5es e dicas<\/b><\/span><\/span><\/span><\/p>\n

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

Devemos observar que a <\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica do resistor depende apenas do <\/b><\/span><\/span><\/span>resistor<\/b><\/span><\/span><\/span> e da <\/b><\/span><\/span><\/span>sua <\/b><\/span><\/span><\/span>temperatura <\/b><\/span><\/span><\/span>e que <\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>W<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>= 1 V.1 A.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Costumamos <\/b><\/span><\/span><\/span>freq\u00fcentemente utilizar m\u00faltiplos do ohm <\/b><\/span><\/span><\/span>\"\" <\/b><\/span><\/span><\/span>1kW<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>= 10<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>W e 1 MW<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>= 10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>W.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Os metais,<\/b><\/span><\/span><\/span> na sua maioria, s\u00e3o <\/b><\/span><\/span><\/span>resistores \u00f4hmicos <\/b><\/span><\/span><\/span>quando <\/b><\/span><\/span><\/span>mantemos constantes suas temperaturas<\/b><\/span><\/span><\/span><\/p>\n

pois, quanto maior a temperatura desses resistores<\/b><\/span><\/span><\/span> <\/b>maior o movimento vibrat\u00f3rio<\/b><\/span><\/span><\/span> de suas mol\u00e9culas e \u00e1tomos, <\/b><\/span><\/span><\/span>dificultando a passagem da corrente el\u00e9trica<\/b><\/span><\/span><\/span>(movimento de el\u00e9trons livres) e <\/b><\/span><\/span><\/span>aumentando assim, sua resist\u00eancia el\u00e9trica.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica de um condutor depende dos pontos<\/b><\/span><\/span><\/span> onde voc\u00ea est\u00e1 <\/b><\/span><\/span><\/span>medindo a diferen\u00e7a de<\/b><\/span><\/span><\/span> <\/b>potencial.<\/b><\/span><\/span><\/span> Assim,\u00a0<\/b><\/span><\/span><\/span>para uma <\/b><\/span><\/span><\/span>mesma tens\u00e3o U<\/b><\/span><\/span><\/span>,<\/b><\/span><\/span><\/span> quanto <\/b><\/span><\/span><\/span>maior for a dist\u00e2ncia entre os dois pontos,<\/b><\/span><\/span><\/span> <\/b>maior ser\u00e1 o valor da resist\u00eancia el\u00e9trica<\/b><\/span><\/span><\/span> e conseq\u00fcentemente <\/b><\/span><\/span><\/span>menor ser\u00e1 o valor da corrente<\/b><\/span><\/span><\/span> <\/b>el\u00e9trica<\/b><\/span><\/span><\/span>\u00a0i,<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>pois, nesse caso, na<\/b><\/span><\/span><\/span>express\u00e3o R=U\/i,<\/b><\/span><\/span><\/span> <\/b>i <\/b><\/span><\/span><\/span>\u00e9 <\/b><\/span><\/span><\/span>inversamente proporcional a R,<\/b><\/span><\/span><\/span> com <\/b><\/span><\/span><\/span>U permanecendo constante..<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

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

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

A <\/b><\/span><\/span><\/span>corrente el\u00e9trica tem sempre sentido do maior para o menor potencial,<\/b><\/span><\/span><\/span> pois, durante o percurso h\u00e1\u00a0 <\/b><\/span><\/span><\/span>\u201cperda\u201d<\/b><\/span><\/span><\/span>, ou seja, <\/b><\/span><\/span><\/span>transforma\u00e7\u00e3o de energia el\u00e9trica em energia t\u00e9rmica \u201cefeito Joule\u201d, ficando o potencial final menor que o inicial..<\/b><\/span><\/span><\/span><\/p>\n

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

Um ohm (1\u2126)<\/b><\/span><\/span><\/span> \u00e9 o valor da <\/b><\/span><\/span><\/span>resist\u00eancia el\u00e9trica<\/b><\/span><\/span><\/span> entre dois pontos P e Q de um condutor quando, <\/b><\/span><\/span><\/span>sob diferen\u00e7a de potencial de 1 volt.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Chama-se s<\/b><\/span><\/span><\/span>upercondutividade <\/b><\/span><\/span><\/span>ao fen\u00f4meno pelo qual a <\/b><\/span><\/span><\/span>resist\u00eancia de certos metais se anula<\/b><\/span><\/span><\/span> \u00e0 <\/b><\/span><\/span><\/span>temperaturas muito baixas.<\/b><\/span><\/span><\/span><\/b><\/p>\n

Chama-se <\/b><\/span><\/span><\/span>supercondutor ao condutor que est\u00e1 com resistividade (proporciona \u00e0 resist\u00eancia) nula.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0A <\/b><\/span><\/span><\/span>temperatura<\/b><\/span><\/span><\/span> em que o metal se torna <\/b><\/span><\/span><\/span>supercondutor \u00e9 pr\u00f3xima do zero absoluto<\/b><\/span><\/span><\/span> e varia de metal para metal.<\/b><\/span><\/span><\/span><\/p>\n

At\u00e9 o presente, <\/b><\/span><\/span><\/span>poucos s\u00e3o os metais que revelaram o fen\u00f4meno.<\/b><\/span><\/span><\/span> <\/b>Exemplos: merc\u00fario, que se torna supercondutor a 4,19 K; o t\u00f3rio, a 1,4K; o chumbo, a 7,2K.<\/b><\/span><\/span><\/span><\/p>\n

\"lei<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\u00a0Um <\/b><\/span><\/span><\/span>chuveiro el\u00e9trico<\/b><\/span><\/span><\/span>, \u00e0s vezes <\/b><\/span><\/span><\/span>demora um pouco para come\u00e7ar a aquecer,<\/b><\/span><\/span><\/span> pois, \u00e9 a <\/b><\/span><\/span><\/span>press\u00e3o da \u00e1gua<\/b><\/span><\/span><\/span> <\/b>liga os contatos el\u00e9tricos atrav\u00e9s de um diafragma.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

 <\/p>\n

Confira os exerc\u00edcios com resolu\u00e7\u00e3o comentada<\/span><\/a><\/h3>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Resistores \u2013 Primeira lei de Ohm \u2013 Pot\u00eancia el\u00e9trica de um resistor Efeito Joule \u00a0Efeito Joule\u00a0\u00a0 num condutor met\u00e1lico, os el\u00e9trons livres da corrente el\u00e9trica, durante suas movimenta\u00e7\u00f5es, sofrem continuamente colis\u00f5es com os \u00e1tomos da rede cristalina desse condutor, transferindo a eles\u00a0 parte de sua energia cin\u00e9tica e, como resultado, os \u00e1tomos do condutor, como um todo, passam a vibrar<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1676,"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-1721","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1721","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=1721"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1721\/revisions"}],"predecessor-version":[{"id":9667,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1721\/revisions\/9667"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/1676"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=1721"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}