The value of electric permittivity of free space is

Three identical charged balls each of charge $2 \,C$ are suspended from a common point $P$ by silk threads of $2 \,m$ each (as shown in figure). They form an equilateral triangle of side $1 \,m$.

The ratio of net force on a charged ball to the force between any two charged balls will be ………..

Two positive point charges of unequal magnitude are placed at a certain distance apart. A small positive test charge is placed at null point, then

Two point charges $A$ and $B$, having charges $+Q$ and $- Q$ respectively, are placed at certain distance apart and force acting between them is $\mathrm{F}$. If $25 \%$ charge of $A$ is transferred to $B$, then force between the charges becomes

Two identical charged particles each having a mass $10 \,g$ and charge $2.0 \times 10^{-7}\,C$ area placed on a horizontal table with a separation of $L$ between then such that they stay in limited equilibrium. If the coefficient of friction between each particle and the table is $0.25$, find the value of $L$.[Use $g =10\,ms ^{-2}$ ]……….$cm$