GR0177 #95



Alternate Solutions 
RusFortunat 20151016 22:17:54  What if we simply use the fact that on the border, or . Applying this to our conditions we get .   fcarter 20081013 17:16:57  Another one where limits are the fast way. For K>1, E>E. For K>inf, E>0. Only answer that satisfies is A.   Mexicana 20071002 17:57:24  Another way to increase your chances of getting it right is by elimination of choices B, C and D since using dimensional analysis only choice A and E have the correct dimensions of electric field ( is dimensionless). If with this you also remember the fact that a dielectric under an applied electric field, induces an internal field so that the total field inside decreases, then only choice A remains (as this is the only one which would decrease the original field ).   herrphysik 20061002 18:42:02  Just use the equation (4.35 in Griffiths) where is the relative permittivity. Plug in the given to get the correct answer.  

Comments 
RusFortunat 20151016 22:17:54  What if we simply use the fact that on the border, or . Applying this to our conditions we get .
RusFortunat 20151016 22:20:53 
D: in preview it was more nice

  johnVay 20131016 19:06:28  dielectics (like in capacitors) increasing rearranging their internal charges to oppose
the E field. in the limit they are conductors where they rearrange perfectly.
the order:
vacuum  dielectic  conductor
dielectrics always scaling the electric field by kappa. this leaves a and b, you need a little more to recognize that B has an extra factor of epsilon   fcarter 20081013 17:16:57  Another one where limits are the fast way. For K>1, E>E. For K>inf, E>0. Only answer that satisfies is A.
f4hy 20091107 00:27:13 
Doesn't (B) satisfy those limits as well?

  Mexicana 20071002 17:57:24  Another way to increase your chances of getting it right is by elimination of choices B, C and D since using dimensional analysis only choice A and E have the correct dimensions of electric field ( is dimensionless). If with this you also remember the fact that a dielectric under an applied electric field, induces an internal field so that the total field inside decreases, then only choice A remains (as this is the only one which would decrease the original field ).
Moush 20100918 15:55:06 
Choice C has the same units as A and E so you can't eliminate it based only on dimensional analysis, but it's intuitive that < .

  Mexicana 20071002 17:52:53  Another way to increase your chances of getting it right is by elimination of choices B, C and D since using dimensional analysis only choice A and E have the correct dimensions of electric field ( is dimensionless).   herrphysik 20061002 18:42:02  Just use the equation (4.35 in Griffiths) where is the relative permittivity. Plug in the given to get the correct answer.  

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