question_answer

A sheet of aluminium foil of negligible thickness is introduced between the plates of a capacitor. The capacitance of the capacitor     AIEEE  Solved  Paper-2003

A) decreases                          

B) remains unchanged

C) becomes infinite

D) Increases

Correct Answer: B

Solution :

Aluminium is a metal, so when we insert an aluminium foil, equal and opposite charges appear on its two surfaces. Since, it is of negligible thickness, it will not effect the capacitance. Alternative Solution From the formula,                     \[C=\frac{{{\varepsilon }_{0}}A}{d-t+\frac{t}{K}}\]             Here, \[K=\infty \] and \[t\to 0\] So,      \[C=\frac{{{\varepsilon }_{0}}A}{d+0}=\frac{{{\varepsilon }_{0}}A}{d}={{C}_{0}}\]