0
$\begingroup$

enter image description here

In the image above the second faint part is the answer to the question c). The answer starts with the word evidently, and I am confused why it is evident. Also, since we are considering a shell, shouldn't it be a 3D form of Delta Dirac function? Is there anything wrong with the answer?

Improve this question
$\endgroup$
2
  • $\begingroup$ It was obviously evident to the person who wrote the answer that a delta function was the way to go. The situation is spherically symmetrical and so $r$, the distance from the origin, is a suitable variable. What do you think the answer should be? $\endgroup$
    – Farcher
    Commented Jan 28, 2017 at 7:54
  • $\begingroup$ Hint: How can you describe a constant charge distribution $\sigma$ on the $xy$-plane? $\endgroup$
    – Raziman T V
    Commented Jan 28, 2017 at 8:23

1 Answer 1

Reset to default
2
$\begingroup$

It is evident because there is no charge anywhere except $r=R$, therefore the charge density will have a $\delta(r-R)$ to capture this. ... and it is indeed $\delta(r-R)$ because this is spherical distribution which depend on the radial coordinate only, rather than all $3$ coordinates, i.e. you are describing a surface (2d) of fixed radius which does not depend on $\theta$ and $\phi$.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.