Two point charges interact electrostatically in different situations
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two point charges interact electrostatically in different situations.
Answer the following questions based on Coulomb’s law.
(a) State Coulomb’s law in words and write its mathematical form for the magnitude of the force between two stationary point charges in vacuum.
(b) Describe how the nature (attractive/repulsive) of the force depends on the signs of the interacting charges.
(c) Charges q1=+4μC and q2=−6μC are kept 0.20m apart in air. Without making a numerical substitution, predict (i) whether the force between them is attractive or repulsive and (ii) whether its magnitude is the same, greater, or smaller than the force that would exist if both charges were positive with the same magnitudes and separation. Justify your answer qualitatively.
(d) If the original pair of unlike charges in part (c) is immersed completely in a medium of relative permittivity εr=5, explain qualitatively how the magnitude of the force will change and give a physical reason for this change.