Charge $Q$ in cavity inside conductor A point charge Q is inside a cavity in an uncharged conductor. Is the force on Q necessarily zero?
The explanation in the answer goes as 

No. For example, if it is very close to the wall, it will induce a charge of the opposite sign on the wall, and it will be attracted.

This sounds weird to me because:-


*

*First of all, it says if Q is very close to the wall, it will induce a charge of the opposite sign on the wall but opposite sign shall develop every time on the inner surface of cavity irrespective of the particle's position inside the cavity.

*Isn't it that getting attracted would signify experiencing a force because of charge's own field since the field inside the cavity is just because of the charge placed [BY GAUSS LAW].
 A: 
First of all, it says if Q is very close to the wall, it will induce a charge of the opposite sign on the wall but opposite sign shall develop every time on the inner surface of cavity irrespective of the particle's position inside the cavity.

Yes, the presence of the charge Q will always induce charges of the opposite sign on the inner wall (field inside the conductor should be zero and thus, Gauss law tells us that the inner surface must have a total of -Q charge). However, if the charge is placed exactly at the centre, the charge distribution over the inner surface is symmetric, so there is no force on the charge. But in all other cases, the charge will experience a force due to the induced charges on the inner surface.

Isn't it that getting attracted would signify experiencing a force because of charge's own field since the field inside the cavity is just because of the charge placed [BY GAUSS LAW].



*

*Firstly, field as calculated by Gauss law is due to all the charges, not just the ones enclosed by the closed surface over which we apply Gauss law.

*The induced charges are exerting a force on Q. As far as i know, a charge does not exert a force on itself.

