A point charge $+Q$ is positioned at the centren of the base of a square pyramid as shown. The flux through one of the four identical upper faces of the pyramid is
$\frac{Q}{{16{\varepsilon _0}}}$
$\frac{Q}{{4{\varepsilon _0}}}$
$\frac{Q}{{8{\varepsilon _0}}}$
None of these
A parallel plate capacitor has plates with area $A$ and separation $d$ . A battery charges the plates to a potential difference $V_0$. The battery is then disconnected and a dielectric slab of thickness $d $ is introduced. The ratio of energy stored in the capacitor before and after the slab is introduced is
Two identical small spheres carry charge of $Q_1$ and $Q_2$ with $Q_1>>Q_2.$ The charges are $d$ distance apart. The force they exert on one another is $F_1.$ The spheres are made to touch one another and then separated to distance $d$ apart. The force they exert on one another now is $F_2.$ Then $F_1/F_2$ is
An insulator plate is passed between the plates of a capacitor. The the displacement current
Five indentical capacitor plates, each of area $A,$ are arranged such that adjacent plates are at distance $d$ apart. The plates are connected to a source of $emf$ $V$ as shown in fig. Then the charges $1$ and $4$ are, respectively :-
Two point charges $+q$ and $-q$ are held fixed at $(-d, 0)$ and $(+d, 0)$ respectively of a $(x, y)$ coordinate system. Then