Experiências de Indução.

B B dA r r

Cuidado !!!

B dA 0 r r

Ñ

Lei de Faraday

Bd

dt

http://ocw.mit.edu/ans7870/8/8.02T/f04/visualizations/faraday/15-inductance/1_edit.wmv

http://ocw.mit.edu/ans7870/8/8.02T/f04/visualizations/faraday/15-inductance/15-1_wmv320.html

A fem induzida A fem induzida em uma espira em uma espira é dada pela é dada pela taxa de taxa de variação do variação do fluxo fluxo magnético, magnético, com o sinal com o sinal negativo, negativo, através da área através da área delimitada delimitada pela espira.pela espira.

Bd

dt

Repare que o campo magnético gerado se opõe a variação do que o gera.

Para N espiras:Bd

Ndt

Lei de Lenz

Want A More Exciting Experiment?A more elaborate experiment that demonstrates the same scientific principles can be done with a solenoid wrapped around a pop can. When the switch is closed. a capacitor in the circuit is discharged through the solenoid. Since the current varies in time, the magnetic field in the solenoid and the magnetic flux defined in the solenoid will vary in time. This variable flux also passes through the can inside the solenoid, inducing in it a current in opposite direction of the current through the solenoid (Lenz's Law). The two antiparallel currents repel each other, and since the solenoid is fixed the can will be crushed.

http://www.ndt-ed.org/TeachingResources/NDT_Tips/LenzLaw.htm

You Tube: http://www.youtube.com/watch?v=wt3It6d1o_Y

Força Eletromotriz Produzida pelo Movimento

As cargas se acumulam na extremidade da haste até que:

qE qvB E vB

abV EL vBL

A haste funciona como um gerador de fem.

vBL

IR vBL

d v B dl rrr

g v B dl rrr

gÑLembrete: Não vale para condutores em repouso em um campo magnético variável.

Campos Elétricos Induzidos

B BA nIA 0

Bd dInA

dt dt

0

Campos Elétricos Induzidos

BdE dl

dt

rrgÑ

Faraday's law of induction gives the relation between the rate of change of the magnetic flux through the area enclosed by a closed loop and the electric field induced along the loop:

whereΦB is the magnetic flux through the area A described by the second equationE is the electric field generated by the magnetic fluxs is a closed path in which current is induced, such as a wire.Or, in differential form in terms of magnetic field B:Note the negative sign; it is necessary to maintain conservation of energy. It is so important that it even has its own name, Lenz's law.

I. Gauss' law for electricity

                     

Equações de Maxwell

I. Gauss' law for magnetism

                   

III. Faraday's law of induction

                          

IV. Ampere's law

                                           

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/maxeq.html#c2

Ache o erro:

http://lizti.br.tripod.com/maxwell_na_forma_int.htm

http://plato.if.usp.br/~fap2292d/NotasDeAula3.pdf

Equações de Maxwell

xt

0 x 0t

DD ρ H J

BB E

Exercícios

Todos os problemas do capítulo 30.