Two small balls having equal positive charge q Coulomb are suspended by two insulating strings of equal length L metre from a hook fixed to a stand. The whole set up is taken in a satellite into space where there is no gravity. What is the angle between the two strings and the tension in each string?

In a satellite, there is condition of weightlessness.
Therefore, mg = 0.
On account of electrostatic force of repulsion between the balls, the strings would become horizontal.

Therefore, angle between the strings = 180°.

Also, tension in each string = force of repulsion
                
                 $\mathrm{T} = \frac{1}{4\mathrm{\pi }{\in }_0}\frac{{\mathrm{q}}^2}{(2\mathrm{l}{)}^2} \mathrm{N}$

An electric line of force is an imaginary straight or curved path along which a small positive test charge is supposed to move when free to do so.
The tangent at a point on an electric line of force gives the direction of the resultant electric field at that point.
The relative closeness of electric lines of force in a certain region provides us an estimation of the electric field strength in that region.