$729$ small identical spheres each charged to an electric potential $3 \ V$ combine to form a bigger sphere. The electric potential of the bigger sphere is (in $V$)

$A$ charge $+q$ is placed at the origin $O$ of $X-Y$ axes as shown in the figure. The work done in taking a charge $Q$ from $A$ to $B$ along the straight line $AB$ is

Assertion: Electrons move away from a region of higher potential to a region of lower potential.
Reason: An electron has a negative charge.

Three particles,each having a charge of $10\,\mu C$,are placed at the corners of an equilateral triangle of side $10\,cm$. The electrostatic potential energy of the system is.....$J$ (Given $\frac{1}{4\pi\varepsilon_0} = 9 \times 10^9\,N\cdot m^2/C^2$).

$A$ charge $Q$ is placed at each corner of a cube of side $r$. The potential at the centre of the cube is ($\epsilon_0$ = permittivity of free space).

An electron with an initial speed of $4.0 \times 10^6 \, m/s$ is brought to rest by an electric field. The mass and charge of an electron are $9 \times 10^{-31} \, kg$ and $1.6 \times 10^{-19} \, C$, respectively. Identify the correct statement.