The distance between charges $+\mathrm{q}$ and $-\mathrm{q}$ is $2 l$ and between $+2 \mathrm{q}$ and $-2 \mathrm{q}$ is $4 l$. The electrostatic potential at point $P$ at a distance $r$ from centre $O$ is $-\alpha\left[\frac{q l}{r^2}\right] \times 10^9 \mathrm{~V}$, where the value of $\alpha$ is____. (Use $\left.\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{Nm}^2 \mathrm{C}^{-2}\right)$
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Two small equal point charges of magnitude $q$ are suspended from a common point on the ceiling by insulating mass less strings of equal lengths. They come to equilibrium with each string making angle $\theta $ from the vertical. If the mass of each charge is $m,$ then the electrostatic potential at the centre of line joining them will be $\left( {\frac{1}{{4\pi { \in _0}}} = k} \right).$
Two condensers of capacities $1\,\mu F$ and $2\,\mu F$ are connected in series and the system is charged to $120\;volts$. Then the $P.D.$ on $1\,\mu F$ capacitor (in $volts$) will be
A network of four capacitors of capacity equal to ${C_1} = C,\,\,{C_2} = 2C,\,{C_3} = 3C$ and ${C_4} = 4C$ are conducted in a battery as shown in the figure. The ratio of the charges on ${C_2}$ and ${C_4}$ is
A particle of mass $m$ and charge $q$ is kept at the top of a fixed frictionless sphere. $A$ uniform horizontal electric field $E$ is switched on. The particle looses contact with the sphere, when the line joining the center of the sphere and the particle makes an angle $45^o$ with the vertical. The ratio $\frac{qE}{mg}$ is :-
This question contains Statement$-1$ and Statement$-2$. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement$-1$ : For a charged particle moving from point $P$ to point $Q$, the net work done by an electrostatic field on the particle is independent of the path connecting point $P$ to point $Q$.
Statement$-2$ : The net work done by a conservative force on an object moving along a closed loop is zero.
A parallel plate capacitor is charged to a certain potential and the charging battery is then disconnected. Now, if the plates of the capacitor are moved apart then:
Consider the combination of $2$ capacitors $C _{1}$ and $C _{2},$ with $C _{2}> C _{1},$ when connected in parallel, the equivalent capacitance is $\frac{15}{4}$ time the equivalent capacitance of the same connected in series. Calculate the ratio of capacitors, $\frac{ C _{2}}{ C _{1}}$
A series combination of three capacitors of capacities $1\,\mu \,F,\,2\,\mu \,F$ and $8\,\mu \,F$ is connected to a battery of $e.m.f.$ $13\, volt$. The potential difference across the plates of $2\,\mu \,F$ capacitor will be.....$V$
Three charges, each $+q,$ are placed at the comers of an isosceles triangle $ABC$ of sides $BC$ and $AC, 2a.$ $D$ and $E$ are the mid-points of $BC$ and $CA.$ The work done in taking a charge $Q$ from $D$ to $E$ is