# What does a dielectric medium inside a capacitor do to an electric field

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Thread starter 5 years ago
#1

I think the answer is D because of the equation, C= (permittivity of free space x A)/D.

But I don't understand what a dielectric medium inside a capacitor does to an electric field.
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5 years ago
#2
The correct answer is C
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5 years ago
#3
The correct answer is C

A) I am pretty sure, by definition, all capacitors already contain a dielectric medium

B) The electric field across a capacitor (when at least partially charged) is uniform.

C) C = q/V

V = W/q

C = q*q/W

W = Fd

C = q*q/Fd

D) Increasing distance would cause capacitance to decrease

E) Current does not flow between the positively and negatively charged plates
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Thread starter 5 years ago
#4
(Original post by Liquid27)
The correct answer is C
Ok, from which equation?
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5 years ago
#5
(Original post by Airess3)
Ok, from which equation?
Please see next post - let me know if I haven't been clear
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5 years ago
#6
(Original post by Liquid27)
The correct answer is C

A) I am pretty sure, by definition, all capacitors already contain a dielectric medium
They don't; you can have a perfectly good capacitor with a vacuum between the plates. A is wrong because a dielectric *decreases* the electric field strength between the plates. (Polar molecules align themselves with charges anti-parallel to the plates, so their E field vectors point in the opposite direction to the polarising field).
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5 years ago
#7
(Original post by atsruser)
They don't; you can have a perfectly good capacitor with a vacuum between the plates. A is wrong because a dielectric *decreases* the electric field strength between the plates. (Polar molecules align themselves with charges anti-parallel to the plates, so their E field vectors point in the opposite direction to the polarising field).
You can define a vacuum as being a dielectric - It is a question of semantics
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5 years ago
#8
(Original post by Liquid27)
You can define a vacuum as being a dielectric - It is a question of semantics
Well, you could, and I think physicists are more likely to do so than engineers, but it's pretty clear from the question that they were referring to something other than a vacuum when they use the term "dielectric" in this context. (I do note however, that you used the term "dielectric medium" as opposed to "dielectric material" which is what I (mis)read - I'll concede that a vacuum is acceptable as a dielectric *medium*)
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