Capacitor Charge Calculation with Dielectric Insertion

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The discussion focuses on calculating the new charge stored on a capacitor's positive plate after inserting a dielectric material that generates an opposing electric field of -0.30E. Participants clarify that the capacitor remains connected to a battery, maintaining a constant voltage, which affects the electric field and charge relationship. They explore the relationship between electric displacement, surface charge density, and the dielectric constant, concluding that the new charge will increase due to the dielectric's presence. The conversation also emphasizes understanding how the electric field changes with the dielectric and the implications for charge storage. Overall, the participants aim to derive the new charge while addressing misconceptions about electric field equations.
  • #31
Callix said:
Well logically I would suppose not then, since C=q/V and we already know V is constant because of the battery, so q must change. Adding dielectrics help increase C, so that means q increases as well.

So before, were you saying that E=E1-(-E2)? Or E=E1+(-E2), because it seems like you're hinting that it's the first, which in that case it would be by a factor of 1.7.
It is the first, E1=E+E2, but E2 is the field of the dipoles, which is 0.3E, if the E2 means the magnitude of the dipole field.
 
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  • #32
ehild said:
It is the first, E1=E+E2, but E2 is the field of the dipoles, which is 0.3E, if the E2 means the magnitude of the dipole field.

Right, so then it would increase by a factor of 1.7, so
σ'=1.7σ=1.7ε0E1.
And that is the surface charge density on the dielectric?
 
  • #33
Callix said:
Right, so then it would increase by a factor of 1.7, so
σ'=1.7σ=1.7ε0E1.
And that is the surface charge density on the dielectric?
Why 1.7? It is wrong.
 
Last edited:

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