Physics

Problem

Two identical point charges kept

0.30\,\text{m}

apart experience an electrostatic force of

1.0\,\text{N}

in vacuum and

0.25\,\text{N}

when the region between them is completely filled with an insulating oil. a. (i) Derive an expression that relates the relative permittivity

\varepsilon_r

of the oil to the magnitudes of the forces measured in vacuum and in the oil. b. (ii) Using the given data, calculate the numerical value of

\varepsilon_r

for the oil. c. (iii) Keeping the charges the same, the separation in oil is now increased to

0.60\,\text{m}

. Predict the new magnitude of the force between the charges.