- #1
Shell_E
- 3
- 1
So I was reading Jackson's discussion on Image charge method of a grounding sphere.
He first assumed an image charge q inside Sphere with radius a, so the potential for real change and image charge is
.
The by set potential equal to 0 at x=a, he solved q' and y'
Then he can get potential, thus get E field, also can get force on real charge q.
Then he figured out surface charge density by:
Then he mentioned that the force on unit area da is just :
So this is the part I don't get, I understand that σ *da = dq is the charge on area da, but what is the rest part? I don't really get why dF = dq * (σ /2ε ), is that indicate the E field at da is (σ /2ε )? if so, how do we get this?
Thank you!
He first assumed an image charge q inside Sphere with radius a, so the potential for real change and image charge is
The by set potential equal to 0 at x=a, he solved q' and y'
Then he can get potential, thus get E field, also can get force on real charge q.
Then he figured out surface charge density by:
Then he mentioned that the force on unit area da is just :
So this is the part I don't get, I understand that σ *da = dq is the charge on area da, but what is the rest part? I don't really get why dF = dq * (σ /2ε ), is that indicate the E field at da is (σ /2ε )? if so, how do we get this?
Thank you!