IIT JEE , AIEEE Forum - Physics , Electricity

sneha_91

a positive charge is placed at the center of a hollow shell. negative charge is uniformly distributed on it's outer surface.discuss the field for both inside and outside the shell

nitiagr

inside the shell the field will be 0

in case of charge outside shell consider a gaussian surface and apply gauss theorem

Eq/4pi e₀r^2

indrajeet_bariar

u havent specify whether the +ve charge and negative charge given are equal or not.If the positive charge at the centre and negative charge distributed are equal then by applying GAUSS theorum, the field inside the hollow sphere

CASE 1- INSIDE THE SPHERE at a point at distance r < R, where R is radius of sphere

                 E = q/4pie0r^2

CASE 2 - ON THE SURFACE OF THE SPHERE

                 E = 0

CASE 3 - OUTSIDE THE SPHERE

                 E = 0

THIS IS THE RIGHT EXPRESSION AS FAR AS I BELIEVE,PLZ... VOTE IF I M RIGHT.

mukundmadhav

Agree with indrajeet..

indrajeet_bariar

HEY GUYS IF U AGREE WITH ME THEN PLZ... VOTE. I HAVE JUST JOINED THE SITE N NEED THE VOTING. PLZ... VOTE.

rishipratimm

@indrajeet...
this site has lots of intelligent people....
they will surely judge your worth and vote you if u really deserve it....
so,there's no need to publicly ask 4 votes,dude....
jst keep answerin,votes will come...

sneha_91

can u people explain ur answers...y isn't the field inside zero

jinu.coolboy

Plz give the charges on the sphere and point.

jinu.coolboy

I think we cannot apply Gauss's theorem because the field from a given pt. charge is not passing through the sphere . The field lines just terminate on the sphere.

indrajeet_bariar

@SNEHA
HEY SNEHA. U ASKED WHY THE FIELD INSIDE THE SPHERE IS NOT ZERO.OK, LETS SUPPOSE A POINT P INSIDE THE SPHERE. NOW IF U DRAW A GAUSSIAN SURFACE (i.e. A SPHERE, U WILL FIND THT IT HAS ENCLOSED THE CHARGE +Q WHICH U HAVE KEPT AT THE CENTRE. sINCE THE GAUSSIAN SURFACE THROUGH THE POINT P IS ENCLOSING A CHARGE U NEVER SAY THT THE FIELD AT THE POINT WILL BE ZERO COZ. SOME FLUX IS ALWAYS PASSING THROUGH THE SURFACE AS SPECIFIED BY GAUSS LAW.
SATISFIED??? IF STILL IN DOUBT U CAN ASK MORE.
PLZ... RATE IF SATISFIED

indrajeet_bariar

@ jinu.coolboy
HEY DUDE.HOW CAN U SAY THT V CANNOT APPLY GAUSS LAW. SEE,U ARE SAYING ITS BECAUSE FIELD FROM GIVEN CHARGE IS NOT PASSING THROUGH THE SPHERE.N U R SAYING THT THE LINES OF FORCES JUST TERMINATE AT THE SPHERE. OK NOW TELL ME HOW U CAN SAY SO, WITHOUT APPLYING GAUSS THEORUM. AND IF U ALREADY KNOW THE ELECTRIC FIELD AT THE SPHERE THEN WHTS THE NEED OF THIS QUESTION. JUST TELL US HOW U CAME TO THIS CONCLUSION WITHOUT APPLYING GAUSS LAW. I WOULD ALSO LIKE TO KNOW THIS NEW METHOD.ACTUALLY WHT U R DOING IS JUDGING THE ELECTRIC FIELD BEFORE APPLYING GAUSS THEORUM, EVEN WHEN U R APPLYING THE LAW TO FIND THE SAME. IF U ALREADY KNOW THEN WHTS THE NEED OF GAUSS THEORUM. HOPE U UNDERSTOOD MY QUESTION.

jinu.coolboy

OK THANKS FOR THE CORRECTION.AND WHAT ABOUT THE FIELD OUTSIDE THE SPHERE?

indrajeet_bariar

@jinu.coolboy
AS FAR AS FIELD OUTSIDE THE SPHERE IS CONCERNED AS I ALREADY STATED IT WILL BE ZERO. JUST TAKE A POINT P OUTSIDE THE SPHERE AND DRAW A SPHERICAL GAUSSIAN SURFACE THROUGH IT.U WILL FINE THT THE NET CHARGE ENCLOSED INSIDE THE GAUSSIAN SURFACE IS ZERO AND HENCE THE FIELD AT THT POINT IS ZERO.

jinu.coolboy

But there is some field of spherical shell outside the surface.

indrajeet_bariar

@jinu.coolboy
DEFINITELY NOT.OK.I HOPE U MUST HAVE STUDIED THT FOR A HOLLOW CHARGED SPHERE AT A POINT OUTSIDE THE SPHERE , ALL THE CHARGE CAN BE CONSIDERED TO BE CONCENTRATED AT THE CENTRE OF THE SPHERE.SO NOW WHEN A POINT OUTSIDE THE SPHERE IS CONCERNED, THE PROBLEM REDUCES TO
" A POSITIVE CHARGE +Q AND A NEGATIVE CHARGE -Q ARE KEPT AT THE SAME POINT. WHT SHOULD BE THE FIELD AT A POINT P AT A DISTANCE R.I KNOW ITS NOT POSSIBLE COZ. TWO PARTICLES CANNOT OCCUPY A SAME POSITION SIMULTANEOUSLY BUT FOR NOW V ARE ONLY ASSUMING. NOW IF U SEE IT, THE FIELD AT P DUE TO POSITIVE CHARGE WILL BE OUTWARDS AND THT DUE TO NEGATIVE CHARGE WILL BE INWARDS AND BEING EQUAL IN MAGNITUDE WILL CANCEL EACH OTHER. THHUS THE FIELD WILL BE ZERO. THIS ALL WHT I HAVE EXPLAINED U IS BASED ON THE CONCEPT V HAVE STUDIED THT" FOR A HOLLOW CHARGED SPHERE AT A POINT OUTSIDE THE

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