State for each of the following statements whether it is True or False and justify your answer in each case with proper reasoning (no calculation is expected).
(i) The principle of superposition fails if the medium between charges is partly conducting.
(ii) If two equal positive point charges are placed anywhere in space, there always exists at least one point on the straight line joining them where the net electrostatic force on a third positive test charge is zero.
(iii) The vector symbol r in Coulomb’s law may be replaced by the scalar distance r without affecting the direction of the calculated force.
(iv) In a system of three collinear charges, if the algebraic sum of the charges is zero, the net electrostatic force on each charge is necessarily zero.
a. (i) Superposition in partly conducting medium
b. (ii) Zero-force point for two like charges
c. (iii) Role of vector r versus scalar r
d. (iv) Force implications of zero net charge