A point charge QC is enclosed in a sphere of radius a with surface charge density ρC/m2.The problem is to find the net flux density at a spherical surface of radius b>a.Will the total charge enclosed be taken as Q+4∏ρa2 (it is square of a)? Will not the enclosed point charge induce a negative charge on sphere of radius a making the total charge enclosed equal to Q+4∏ρa2-Q?Please clarify..

 

How can the point charge induce a net charge on the enclosing sphere? Where would the charge go and/or come from? It can induce a charge separation within the enclosing sphere, but it can't cause charge to appear or disappear.