Dielectric Polarization and Electric Dipole Moment

The collection of physical phenomena associated with the presence and motion of matter with an electric charge is known as electricity. Lightning, static electricity, electric heating, electric discharges, and many other popular phenomena are all related to electricity.

An electric field is generated by the presence of an electric charge, which can be positive or negative. A magnetic field is generated by the movement of electric charges, which is known as an electric current.

Electric Charge

The presence of charge causes an electrostatic force, in which charges exert a force on each other, an effect that was recognized in antiquity but not fully understood. Touching a light ball suspended from a string with a glass rod that has been charged by rubbing with a cloth will charge it. When a similar ball is charged with the same glass rod, it repels the first: the charge serves to separate the two balls. Two balls charged with a rubbed amber rod repel each other as well. When one ball is charged by a glass rod and the other by an amber rod, the two balls are attracted to each other.

Electric Current 

An electric current is the movement of an electric charge, and its strength is normally measured in amperes. A current is made up of all moving charged particles, the most common of which are electrons. Nevertheless, any charge in motion is a current. Electrical current can pass through certain objects, such as electrical conductors, but not through an electrical insulator.

Electric Dipole Moment

The electric dipole moment is a measurement of a system's overall polarity or the separation of positive and negative electrical charges within it. The coulomb-meter (Cm) is the SI unit for electric dipole moment; however, the debye is a widely used unit in atomic physics and chemistry (D).

The first-order concept of the multipole expansion defines an electric dipole in theory; it consists of two equal and opposite charges that are infinitesimally close together, even though actual dipoles have separated charges.

Point charges are charged point particles with an electric charge. An electric dipole is made up of two point charges, one with charge +q and the other with charge q, separated by a distance d. (a simple case of an electric multipole). The electric dipole moment, in this case, has a magnitude of p=qd

and is driven from the negative to the positive charge. Since this quantity is the distance between either charge and the center of the dipole, some authors can break d in half and use s = d/2, resulting in a factor of two in the description.

Since a quantity with magnitude and direction, such as the dipole moment of two point charges, can be expressed in vector form, a better mathematical concept is to use vector algebra.

P=qd

where d denotes the vector of displacement from the negative to the positive charge. Also, the electric dipole moment vector p points from the negative to the positive charge.

The electrical point dipole, which consists of two (infinite) charges that are only infinitesimally separated but have a finite p, is an idealization of this two-charge system. This value is used to calculate the polarization density.

Dielectric

An electrical insulator that can be polarized by an applied electric field is known as a dielectric (or dielectric material). When an electric field is applied to a dielectric material, electric charges do not flow through it as they would in an electrical conductor, but instead change slightly from their average equilibrium positions, resulting in dielectric polarization. Positive charges are displaced in the direction of the field by dielectric polarization, whereas negative charges move in the opposite direction (for example, if the field is moving in the positive x-axis, the negative charges will shift in the negative x-axis). This induces an internal electric field within the dielectric, which decreases the total field. As weakly bound molecules make up a dielectric, the molecules become polarized and reorient so that their symmetry axes match with the field.

Dielectric properties are the analysis of how electric and magnetic energy is stored and dissipated in materials. Electronics, optics, solid-state physics, and cell biophysics all depend on dielectrics to describe different phenomena.

Dielectric Polarization

A substance is made up of atoms in the traditional approach to the dielectric model. Each atom is made up of a cloud of negative charge (electron) that is bound to and surrounds a positive point charge in the center. The charge cloud is skewed in the presence of an electric field.

Using the superposition theorem, this can be reduced to a simple dipole. The dipole moment is a vector quantity that characterizes a dipole. The action of the dielectric is determined by the interaction between the electric field and the dipole moment. The atom returns to its original state when the electric field is withdrawn. The time it takes to do so is referred to as the relaxation time; it is an exponential decay. 

The behavior of the dielectric is determined by the relationship between the electric field E and the dipole moment M, which can be described by the function F defined by the equation:

M=F(E)