Two point charges (at ) and (at ) are embedded in the following arrangement
PHYSICS · Multi-part · CBSE · Physics · Electric Charges and Fields · Electric Charges and Fields
Problem
Two point charges +Q (at x=0) and +4Q (at x=L) are embedded in the following arrangement.
• From x=0 to x=d (d<L) the space is filled with a dielectric material of relative permittivity k.
• From x=d to x=L and everywhere else, the medium is air.
(i) Taking the region x>0 on the common line of the charges, write separate expressions for the magnitudes of the electric fields due to each charge at a general point P located at x>0, clearly indicating which permittivity is to be used in each region.
(ii) Establish the condition for the electric field to be zero at P and hence obtain a single algebraic equation whose solution gives the possible position(s) of the null point.
(iii) Solve the equation obtained in part (ii) to find the location of the null point for the special case k=5, Q=2μC, L=0.60m, d=0.20m.
(iv) Discuss how the position of the null point shifts qualitatively as the dielectric constant k is increased while all other parameters remain fixed.