dielectric concept question

[nickelbackfan]

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Does anyone know why increasing the dielectric constant would increase the capacitance conceptually?


Thanks

 

[farnell]

So the dielectric material can be thought of as how well a material can hold an electric charge. But we wouldn't expect a 10 by 10m sheet of copper to hold the same charge as a 1 by 1m sheet of copper, right? In the capacitance equation, capacitance increases if the dielectric increases because that means it can hold more charge. When calculating capacitance, however, we take both the dielectric and size of the material into consideration. Does this help?

 

[nickelbackfan]

I guess I'm just trying to figure out why the dielectric constant would increase capacitance but also decrease the Force between them, but I think thats like comparing apples to oranges

 

[Me911]

The dielectric constant (k) is "the ratio of electrical force between two charges when they are in a vacuum compared to when they are in a medium...Dielectric behavior results from a medium's polar nature, including its ability to assume an induced dipole" (p126 TBR Physics).

Essentially the molecules in a strongly polar medium between the plates of a capacitor will be induced by the charges on the plates of capacitor to reorient themselves (the polar molecules) along the lines of the electric field produced by the capacitor. So polar molecules that are haphazardly arranged, will be arranged with their partially negative ends pointing to the positively charged capacitor plate and their partially positive ends will be pointing to the negatively charged capacitor plate. The alignment of the polar molecules in the medium with the capacitor plates actually weakens the net electric field caused by the capacitor. "The polar medium aligns in such a way as to offset, and in doing so, diminish the magnitude of charge on each plate" (126). This allows more charge to be stored on the plate...and thus increase the capacitance of the capacitor (C=Q/V).

Hope this is kinda what you were looking for...

 

[shaboobly]

idk if this is right or not, but the way i always thought about it is it's like an insulator (how insulation keeps the heat inside a house). when you add a dielectric material it is keeping the charges separated more (insulated so to say) which increases the amount of charge on the plates and thus the capacitance.