Two fixed point charges and are separated by in a medium of relative permittivity
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two fixed point charges q1 and q2 are separated by 12cm in a medium of relative permittivity εr=4. The magnitude of the force between them is measured as 0.400N. The charges are now transferred without loss to a vacuum and their separation is increased to 18cm. Answer the following:
(a) Calculate the magnitude of the force between the charges in the new situation.
(b) Find the ratio Fvacuum/Fmedium, where Fvacuum is the force in vacuum at 18cm separation and Fmedium is the original force in the dielectric at 12cm separation.
(c) Comment briefly on whether the change in medium or the change in separation has the greater effect on the force magnitude in this case.