At a distance of from an unknown point charge kept in a medium of relative permittivity
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
At a distance of 0.20m from an unknown point charge kept in a medium of relative permittivity εr=4, the electric potential is measured to be 180V.
(i) Determine the magnitude and sign of the unknown charge.
(ii) Using your result from (i), calculate the potential at a point situated 0.50m away from the charge in the same medium.
(iii) If the medium between the charge and both observation points were suddenly replaced by air, explain qualitatively how the potentials at the two points would change.