Electric Force, Field, and Potential

Two protons are placed near each other. Which of the following statements is true regarding the electric force between them?

A positive charge of +4q and a negative charge of -q are separated by a certain distance. Which of the following statements is true about the magnitudes of the electric forces between them?

Three charges are arranged in a straight line. Charge $q_1 = +2,\mu C$ is at $x = 0, m$, charge $q_2 = -3,\mu C$ is at $x = 0.2, m$, and charge $q_3 = +4,\mu C$ is at $x = 0.5, m$. What is the net force on $q_1$ due to the other two charges?

At the atomic level, which force is significantly stronger?

Two objects, one with a charge of $+5,\mu C$ and a mass of 2 kg, and another with a charge of $-5,\mu C$ and a mass of 2 kg, are separated by a distance of 1 meter in space. Calculate the electric and gravitational forces between them and determine which force dominates.

A parallel-plate capacitor has a vacuum between its plates. If a material with a high electric permittivity is inserted between the plates, how does the electric field between the plates change (assuming the charge on the plates remains constant)?

How does electric permittivity differ between conductors and insulators?

Two point charges, $q_1 = +3 \times 10^{-6} C$ and $q_2 = -4 \times 10^{-6} C$, are separated by a distance of 0.2 meters. Calculate the electric force between them.

Two identical charged spheres, each with mass $m = 0.01 kg$, are suspended by strings of length $L = 0.3 m$ from a common point. The strings make an angle of $\theta = 5°$ with the vertical. Calculate the charge $q$ on each sphere.