Three capacitors $1, 2$ and $4\,\mu F$ are connected in series to a $10\, volts$ source. The charge on the plates of middle capacitor is

A parallel plate capacitor with air between the plates has a capacitance of $9\, pF$. The separation between its plates is $'d'$. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant $K_1=3$ and thickness $\frac{d}{3}$ while the other one has dielectric constant $K_2 = 6$ and thickness  $\frac{2d}{3}$. Capacitance of the capacitor is now….$pF$

The conducting spherical shells shown in the figure are connected by a conductor. The capacitance of the system is

Two masses $M_1$ and $M_2$ carry positive charges $Q_1$ and $Q_2$, respectively. They are dropped to the floor in a laboratory set up from the same height, where there is a constant electric field vertically upwards. $M_1$ hits the floor before $M_2$. Then,

A negative charged particle is released from rest in a uniform electric field. The electric potential energy of charge