Suppose the charge of a proton and an electron differ slightly. One of them is $-e,$ the other is $(e + \Delta e).$ If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distanced (much greater than atomic size) apart is zero, then $\Delta e$ is of the order of $[$ Given: mass of hydrogen $m_h = 1.67 \times 10^{- 27}\,\, kg]$

Consider three point objects $P, Q$ and $R \cdot P$ and $Q$ repel each other, while $P$ and $R$ attract. What is the nature of force between $Q$ and $R$ ?

In hydrogen like system the ratio of coulombian force and gravitational force between an electron and a proton is in the order of:

Force between two identical spheres charged with same charge is $F$. If $50\%$ charge of one sphere is transferred to second sphere then new force will be

Two charged spheres separated at a distance $d$ exert a force $F$ on each other. If they are immersed in a liquid of dielectric constant $2$, then what is the force (if all conditions are same)

Two point charges $3 \times 10^{-6} \,C$ and  $8 \times 10^{-6} \, C$ repel each other by a force of  $6 \times 10^{-3} \, N$. If each of them is given an additional charge $-6 \times 10^{-6} \, C$, the force between them will be