## yrelhan4 2 years ago flux problem?

1. yrelhan4

|dw:1356550535697:dw| if a charge q is placed at the point M in the diagram, the flux caused through the sphere?

2. rajathsbhat

is the charge placed on the sphere?

3. yrelhan4

point m is halfway between o and o1. o and o1 are on peripherry of ring and sphere respectively.. they are like in a strt line.. the sphere and the ring are symmetrical and o and o1 lie on the diameter..

4. yrelhan4

answer is $4q/3$

5. yrelhan4

3epsilon*

6. yrelhan4

the flux in the sphere.. i'm sorry.. wanted to write something else. just messed up..

7. rajathsbhat

is it a metal sphere? because if it is, the flux through it is zero...

8. yrelhan4

i dont think it is.. the answer is not zero.. so its not..

9. rajathsbhat

but still, the charge is outside the sphere, isn't it? so q(enclosed)=0. And therefore, the flux though the sphere is zero.

10. yrelhan4

no it isnt outside the sphere.. its at M..

11. rajathsbhat

yeah....i'm not getting the picture here...

12. rajathsbhat

|dw:1356553072695:dw| if you look at the arrangement from the side, is this how it'd look?

13. yrelhan4

no.. they are in the same plane.. intersecting at two points..

14. yrelhan4

should i post a pic from the book?

15. rajathsbhat

Ahhh now i see it, thanks.

16. yrelhan4

just reply if you get it.. i'm going off for now.. i have a similar problem if that would help you.. suppose if the charge is placed uniformly on the ring.. then the part with the sphere is only q/3.. so the flux there wuld be q/3epsilon.. i dont think its of any help.. just in case..

17. rajathsbhat

i think it'd be great if you could post the pic..

18. yrelhan4

just a minute..

19. yrelhan4

20. yrelhan4

try it, and tell me you get it..

21. rajathsbhat

i think the question is flawed. Here's why: the only way you can end up with an answer of $$\Large \frac{4q}{3\epsilon_0}$$ is if there's a charge of +q/3 on the ring. [That makes q(enclosed) = q + (q/3) = 4q/3 and so the flux turns out to be $$\large \frac{4q}{3\epsilon_0}$$.] But that's not what happens, When you place that positive charge (+q) there, the part of the ring on the inside of the sphere becomes negatively charged and the part outside becomes positively charged (Of course, here I'm assuming that the ring and the sphere are not touching each other). So, the net charge inside the sphere is $$\text{q-(something)}$$, which is obviously less than $$\Large \frac{4q}{3}$$.

22. yrelhan4

hmm.. i seem to be getting your point.. thank you!!