a thin metal sheet is placed in the middle of a parallel plate capacitor what will be the effect on capacitance?

 The capacitance will increase by k times , Where k is the dielectric constant of that medium !! :)) !! 

no efect on the capacitANCE as it is metal sheet so its dielectric is infinite and second thing it is thin so it will conduct the flow of current,,

ex.if a thin aluuminiun sheet is b/w the cAPacitor .no effect on capacitance,,

but if the who space b/w thwec apacitor is filled with a metal capacitance becomes infinite...