Chapter 4 Flashcards
Quiz Review (8 cards)
What is the difference between E and D?
E (electric field) depends on both free and bound charges. D (electric displacement field) depends only on free charge and is useful for working with dielectrics.
Why is Gauss’s law written in terms of D instead of E in dielectrics?
Because D only accounts for free charge, it is easier to apply Gauss’s law without worrying about bound charge.
How does polarization create a bound charge?
Bound charge comes from the way dipoles align in a dielectric. Volume bound charge: b=-P. Surface bound charge: b=Pn.
What happens to the electric field when a dielectric is introduced between capacitor plates?
The field decreases because the dielectric reduces the effective charge separation, leading to a weaker electric field inside.
Why does a dielectric reduce the effective field inside a material?
The dipoles in the dielectric oppose the external field, leading to partial cancellation of the field inside the material.
How do the boundary conditions for E and D work at the interface of two dielectrics?
The perpendicular component of D changes if there’s a free charge on the boundary. The perpendicular component of E depends on permittivity differences. The parallel component of E is always continuous.
Why is the parallel component of E always continuous at an interface?
Because if there were a discontinuity, it would create an infinite force on charges, which is unphysical.
What happens when you put a conductor inside a dielectric material?
The conductor completely cancels the electric field inside it. The field outside the conductor is adjusted based on the dielectric properties.
