27: Video Tutor Electroscope in Conducting Shell

INTRO:
First, launch the video below. You will be asked to use your knowledge of physics to predict the outcome of an experiment. Then, close the video window and answer the question at right. You can watch the video again at any point.

<< Attach actual video, if possible. Otherwise, find similar video and attach that one >>
 link : https://mediaplayer.pearsoncmg.com/assets/secs-vtd33_electroscope

-----------------------------------------------------------------------------------------------------
PART A:
As in the video, we apply a charge +Q to the half-shell that carries the electroscope. This time, we also apply a charge –Q to the other half-shell. When we bring the two halves together, we observe that the electroscope discharges, just as in the video. What does the electroscope needle do when you separate the two half-shells again?

• It does not deflect at all
• It deflects the same amount as at end of the video.
• It deflects less than it did at the end of the video.
• It deflects more than it did at the end of the video.

SOLUTION:
<< explanation to be added >>
It does not deflect at all

NOTE: 
The spherical surface has zero net charge after the two halves are brought together. The two half-spheres remain electrically neutral after they are separated.

HINTS:
The half-shell with a charge of –Q has an excess of electrons, and the half-shell with a charge of +Q has an exactly equal deficit of electrons.
What happens when these two charged, conducting half-shells are brought together? What is the net charge of the resulting whole sphere? (Recall that electrons can move through a conductor.)
Will the half-shells have a net charge when you separate them again? If the half-shell with the electroscope needle carries a net charge, the needle will deflect.

-----------------------------------------------------------------------------------------------------