Two charges $q_1$ and $q_2$ are separated by a distance of 30cm. A third charge $q_3$ initially at point C is shown in figure, is moved along the circular path of radius 40 cm from C to D. If the difference in potential energy due to movement of $q_3$ from C to D is $q_3 k/4\pi\varepsilon_0$, the value of K is ($\varepsilon_0$ = permittivity of free space)

A capacitor has capacity C when it's parallel plates are separated by air medium of thickness 'd'. A slab of material of dielectric constant K having area equal to that of plates but thickness $\dfrac{d}{2}$ is inserted between the plates. Capacitance of the capacitor in the presence of slab will be

A galvanometer has resistance G and range Vg. How much resistance is required to read voltage up to V volt?

If the potential difference between points B and D is zero in the given circuit, the value of x is $\dfrac{1}{n}\ \Omega$. The value n is