Two point charges are located at two corners of a rectangle, as shown in the figure. a) What is the electric potential at point \(A ?\) b) What is the potential difference between points \(A\) and \(B ?\)

Understanding electric potential begins with the electrostatic constant, symbolized by the letter 'k' in equations. It's a fundamental value in electrostatics, representing the force of attraction or repulsion between two point charges in a vacuum. The constant has a value of approximately \(8.9875517923 \times 10^9\) Newton meter squared per Coulomb squared (\( N m^2 / C^2 \)).

When we consider its role in calculating electric potential, the electrostatic constant is a proportionality factor that helps us determine how strong the potential is due to a charge at a given point. It essentially allows us to quantify the influence of a charge in creating an electric field around it. A higher charge or a lower radius will increase the electric potential because the charge impacts a greater force over a smaller area.

The electric potential difference, often termed 'voltage,' is a measure of the work done by an electric field in moving a charge from one point to another. It's akin to measuring the effort required to move a ball uphill against gravity. Electric potential is energy per unit charge, whereas electric potential difference is the variance in this energy between two points.

In equations, we denote it as \( \Delta V \) and calculate it as the difference in electric potential between two points, expressed as \( \Delta V = V_A - V_B \) in the exercise example. This concept is vitally important because it shows us how potential energy is transformed when a charge moves within an electric field, and it drives the current flow in electrical circuits.

The superposition principle is a key concept in electrostatics, dealing with scenarios where multiple charges are present. It states that the total electric potential at any point is the algebraic sum of the electric potentials due to individual charges.

For example, in our exercise, the electric potential at point A, denoted as \(V_A\), is calculated by summing the potentials due to each point charge separately, following the formula: \(V_A = \frac{kq_1}{r_1} + \frac{kq_2}{r_2}\). This principle greatly simplifies calculations as it allows us to deal with complex charge distributions by considering one charge at a time. It emphasizes that each charge contributes independently to the total potential, and their individual potentials can be simply added together to find the resultant potential.