A sheet of aluminium foil of negligible thickness is introduced between the plates of a capacitor. The capacitance of the capacitor

Options

A. become infinite
B. increases
C. decreases
D. remain unchanged

Answer

D

Explanation

When the aluminium foil is introduced, we get two capacitors, each of plate separation `d/2` and capacity 2C.
thus, `C=(epsi_(0)A)/(d) and C_(2)=(epsi_(0)A)/(d//2)=2C`
the capacity of each =2C and as they are joined in series
`therefore C_(S)=(2Cxx2C)/(2Cxx2C)=C`
`therefore` The capacitance remains unchanged.