IIT JEE , AIEEE Forum - Physics , Electricity

perin

two particles having charges q and 2q are fixed at equal distance x from the centre of a conducting sphere having zero net charge and radius r. intitially the switch s is open. after the switch is closed the net charge flowing out of the sphere is
a qr/x
b -qr/x
c 3qr/x
d -3qr/x

aggmegha90

whats the answer??

neeraj_agarwal_1990

potential at center due to...
1) q is kq/x
2) 2q is k(2q)/x
Let new charge on sphere be 't' (after earthing)

potential at center due to sphere itself is kt/r

net potential should be 0 after earthing...so..

kq/x + 2kq/x + kt/r=0
=>3q/x + t/r=0
=> t= -3qr/x

so it acquires net -ve charge...this means some +ve charge has flown away from the sphere equal to +3qr/x

so answer should be (C)

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