question_answer

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

A)  decreases                         

B)  remains unchanged

C)  becomes infinite

D)  in creases

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 affect the capacitance. Alternative From the formula \[C=\frac{{{\varepsilon }_{0}}A}{d-t+\frac{t}{K}}\] Here,\[K=\infty \]and \[t\to 0\] So,          \[C=\frac{{{\varepsilon }_{0}}A}{d+0}=\frac{{{\varepsilon }_{0}}A}{d}={{C}_{0}}\]