Yes, electric potential can be negative, which is typically associated with negative charges. A negative electric potential indicates the presence of an attractive force towards the source charge for positive test charges. In scenarios where a negative charge serves as the source charge, the electric potential at points in the surrounding electric field will be negative. This is due to the formula Ve = k×Q/r​, where if Q is negative, Ve will also be negative. It doesn’t signify a reduction in energy but illustrates the direction of the electrostatic force and the type of charge inducing the electric field.

"Work done per unit charge" is a phrase that elucidates the concept of electric potential. It is the amount of work done in moving a unit positive charge from infinity to a specific point in an electric field, against the electric force. The unit of measurement is the volt (V), where one volt represents one joule per coulomb. This notion provides insights into the energy landscape of electric fields, offering a mechanism to evaluate the electric field's influence without considering a specific charge, making it a scalar quantity that is integral in understanding electrostatic interactions.

Distances between charges are inversely proportional to both electric potential energy and electric potential. As the separation increases, both energy and potential decrease and vice versa. This is integral in practical contexts like electronic circuits, where charge separation impacts energy levels and potentials, influencing circuit performance. For instance, minimizing charge separation can amplify potential energy, enhancing energy storage in capacitors. Conversely, increased separation can reduce potentials, mitigating risks of electrical breakdowns or arcing, which is essential in high-voltage applications to ensure safety and equipment integrity.

Electric potential energy is pivotal in understanding the stability of a system of charged particles. Systems with negative potential energy are typically more stable as work is needed to separate the charges, indicating an attractive force exists between them. Conversely, positive potential energy suggests a repulsive force between charges, resulting in a less stable system. These concepts are paramount in areas like molecular physics, where the stability of atomic and molecular structures is influenced by the electric potential energy resulting from the electrostatic forces between charged particles, like electrons and protons.

The electric constant 'k' is a fundamental physical constant that describes the strength of the electrostatic force between two charges. Its value is approximately 9 ×10⁹ N (m²/C²). 'k' is derived from Coulomb's law and is instrumental in converting the qualitative description of electrostatic forces into quantitative terms. It serves as a scaling factor in the equations for electric potential energy and electric potential, directly influencing their magnitudes. A larger 'k' would imply stronger electrostatic forces and, consequently, higher potential energies and potentials for given charges and distances.