# Bound and Free Charge in conductor and dielectric

I am reading an electrodynamics book to grasp the concept of bound and free charge, esp in conductor and dielectric. I got lost with the text on the book. Can anyone please help me understand the concept well?

jtbell
Mentor
I bet some people here could help... what specific questions do you have?

gracy
Dale
Mentor
2020 Award
A free charge can move in response to an externally supplied force while a bound charge cannot.

gracy
gabbagabbahey
Homework Helper
Gold Member
Free charges are free to move about the entire medium, while bound charges are restricted to moving in small 'loops' around whichever molecule/ atom they are bound to.

tiny-tim
in case of a wire carrying a certain amount of charge, say Q, which is insulated by a insulator (dielectric), I read that the bound charge on the outer surface and inner surface of the insulator is equal to each other in magnitude. But I could not derive it myself. My approach was to use Guass's law for D, but i did not get what enclosed free charge was. In such a case, how does the equation $$\rho$$ = $$\rho$$b + $$\rho$$f hold true?