Introdução à Eletrostática
Autor: Profª Denise Almeida | Publicado: 2012-06-06T13:18:00-07:00

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Carga Elétrica

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Para a Eletricidade, interessam
principalmente os prótons e os elétrons, que são partículas dotadas de carga
elétrica.



O
próton e o elétron possuem cargas opostas, sendo o próton (+) e o elétron (-).



Chamamos de carga elementar e o
módulo da carga do elétron ou do próton, pois essas partículas possuem a menor
quantidade de carga elétrica encontrada na natureza. Por meio de experimentos,
verificou-se que a carga elementar e
vale:







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&nbsp;E sua unidade no SI é o Coulomb (C).



Um
corpo eletrizado, isto é, com carga total diferente de zero, possui FALTA ou
EXCESSO de um número n
de ELÉTRONS. Sendo Q
a quantidade de carga elétrica desse corpo, seu módulo será calculado como:



Q
= n.e



Assim, quando RETIRAMOS elétrons de um
corpo, sua carga POSITIVA fica maior que a negativa, e o corpo passa a ficar eletrizado
positivamente.

E quando um corpo GANHA elétrons, a
carga NEGATIVA fica maior que a positiva, e o corpo fica eletrizado negativamente.





Condutores
e Isolantes Elétricos

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Dependendo
da constituição de um corpo, ele pode ser classificado em condutor ou isolante.


=&gt; Nos corpos condutores, as cargas
elétricas se movimentam com relativa facilidade.

=&gt; Nos corpos isolantes, não existe
movimentação das cargas, ou existe com muita dificuldade.



Exemplo de condutores:
metais, ferro, alumínio, cobre, prata, entre outros.



Porque os exemplos citados anteriormente
são classificados como corpos condutores?

- Eles apresentam uma estrutura cristalina
na qual ocorre liberação parcial dos elétrons mais externos, mais os elétrons
não conseguem abandonar o cristal. Isso favorece o movimento das cargas e torna
o corpo condutor.