In a parallel plate capacitor of capacitance C, a metal sheet is inserted between the plates, parallel to them. The thickness of the sheet is half of the separation between the plates. The capacitance now becomes
Answer & explanation
Correct answer: option 2
Before the metal sheet is inserted, $C =\frac{\epsilon_0A}{d}$
After the sheet is inserted, the system is equivalent to two capacitors in series, each of capacitance $C' =\frac{\epsilon_0A}{d/4}$
The equivalent capacity is now 2C.