Electric Fields : Definition, Units, and FAQs

Jul 15, 2022 | Turito Team

electric fields

Overview

A force field is a fictional device that applies forces at specific locations in space to accommodate adversaries confined or shield spacecraft from enemy fire. Students may have read about force fields from science fiction films. Despite being considerably different from what they see in movies, the idea of a field is quite important in physics.

The force that encircles anybody and interacts with others at a distance without any evident physical connection can be conceptualised and mapped as a field. For instance, the gravitational field that the Earth and all other planetary masses are subject to simulates the gravitational pull that would exert on an additional mass at a certain location within the field. English scientist Michael Faraday put forth the idea of electric fields in the nineteenth century.

Knowing the electric field makes it simple to determine the force (direction and magnitude) exerted on any placed electric charge. Electric charge produces an electric field, which indicates the force per charge unit at each position in space surrounding a charge distribution.

What is Electric Field

An electric field, also known as a vector field, can be mathematically defined as the electric charge associated with a given position in space; it is the force per unit charge imposed on a positive test charge at a given position. Electric charge or magnetic fields with variable amplitudes can produce an electric field. The electric field is accountable for attraction forces to keep atomic nuclei and electrons together on an atomic scale.

Coulomb’s law states that a particle at position x1 with electric charge q1 pushes against a particle at position x0 with electric charge q0,

Electric Field 1

Coulomb Law

Where,

r1,0 = The unit vector from point x1 to point x0

ε0 = the electric constant, or absolute permittivity of open space 

When the signs of charges q0 and q1 are the same, the force acting on the objects is positive; the direction is apart from other charges, which may repel one another. Similarly, when the charges have opposite signs, the force becomes negative, and the particles are attracted to one another.

The electric field formula can be defined as the force per unit charge; it can be represented as:

Electric Field 2

The electric field formula can be quickly determined by Gauss’s law, which states that the total energy flow out of a closed path is equivalent to the charge concealed divided by the permittivity.

Or the charge contained by the closed path is equal to 1/ε0 times the total energy flow associated with the surface.

Electric Field 3

Although the Gauss law approach is simpler, students can use Coulomb’s law to compute the formula of electric field strength. In addition, Gauss law is merely a copy of Coulomb’s law. Students can get at Coulomb’s law if they apply the Gauss theorem to a charged object surrounded by a sphere.

How to use Gauss Law to compute the electric field formula?

There are a few steps in these.

  • Students should determine the charge distribution’s geometric symmetry (cylindrical, spherical, or planar).
  • The next step is to identify a gaussian symmetry identical to the symmetry of the geometric arrangement.
  • First, find the summation all along the Gaussian surface to find the flux.
  • Locate the charge bounded by the Gaussian surface.
  • Find the charge dispersion in the electric field and the electric field near the point of charge.

The electric field, also known as a vector field, is connected with the Coulomb force generated by the test charge at each location in the space relative to the source. Students can use the Coulomb force (F) on the test charge (q) to calculate the size and direction of the electric field. If a positive charge creates the field, the electric field will radiate outward, and if a negative charge creates the field, the electric field will radiate inward.

Let’s imagine a vacuum with a point charge Q if another point charge q (test charge) is added at a distance r from charge Q.

vacuum

The point charge Q causes an electric field at point p, which is given by,

Electric Field 4

The accompanying graphic depicts the direction of the electric field caused by a point charge Q. The length of E determines the electric field’s strength. A test charge brought into the vicinity of the source charge Q will inevitably change the original electric field caused by the source charge. Utilising a test charge q that is incredibly small is a straightforward method to avoid this problem.

The notion of an electric field then changes to,

electric field 5

Following this explanation,

the formula of electric field strength caused by point charge Q at point P is,

electric field 6

Electric Field Strength

“Electric field strength is the mathematically described term used for measuring the intensity of an electric field at a specific location.” The electric field units can be expressed in volt per metre (v/m or v m-1). The electric field strength of 1 v/m is represented by the potential difference of one volt between two locations separated by one metre.

Any electrically charged element creates electric field strength. The electric field can affect all the nearby charged elements. The electric charge on an element or object is measured in coulombs, directly related to the electric field strength at a certain distance from that element or object. The field’s intensity decreases with increasing separation from positive charge objects. Since electric field strength is defined as a linear displacement (per metre) instead of a surface area, the field-strength-versus-distance curve is a straight inverse function instead of an inverse-square function (per metre squared).

Electric flux density is another way to represent an electric field’s strength. It is the number of electric flux lines travelling perpendicularly (at right angles) across a certain surface area, typically one square metre. Like electric field strength, the charge on an item is directly proportional to the electric flux density. However, because it is expressed as a surface area (per metre squared) instead of a linear displacement, flux density decreases with distance following the inverse-square law (per metre).

The strength of an electromagnetic field is defined in terms of the intensity of its electric-field component. It is done by scientists and researchers when discussing the radio-frequency field strength at a specific area resulting from sources such as the furthest transmitter, astronomical objects, high electricity wires, computer screens, or kitchen appliances. The units used to describe the formula of electric field strength in this context are often microvolts per metre (V/m or V m -1), nano volts per metre (nV/m or nV m -1), or picovolts per metre (pV/m or PV m -1).

Electric Field Units

The electric field unit (SI unit) is volt/metre.

The electric field, also known as electric field intensity, is the force exerted on positively charged ions (units) positioned in the field. At the same time, an electric potential is the amount of work and effort involved in getting a positively charged unit from infinity to the electric field’s action point. 

According to this justification, an electric potential is created whenever a charged particle passes through an area of an electric field. Therefore, the effort to move a particle equals its electric potential. We may determine the electric potential by dividing the electric field by a displacement vector. 

Conclusion

After going through the article, students must have understood the meaning of electric field, its applications and its formula. It is assumed that the field’s direction corresponds to the force it would apply to a point charge. The electric field radiates outward from a positive point charge, and a negative charge radiates inwards.

The value of E, often known as the electric field, electric field intensity, or electric field strength, just expresses the direction and strength of the electric field. Without any precise information about what generated the field, simply knowing the value of the electric field at a certain location is sufficient to predict what would happen to electric charges nearby. Thus, students must comprehend this topic well to learn further knowledge effectively!

Frequently Asked Questions 

1. Describe the concept beneath quantum field theory.

Ans. Quantum field theory is a corpus of physical concepts that combines relativism and quantum mechanics to explain how subatomic particles behave and interact using a range of force fields. Quantum chromodynamics, which represents the interactions of protons and the strong force, and quantum electrodynamics, describes the interactions of electromagnetic force and electrically charged ions theories.

2. What is a magnetic field?

Ans. A magnetic field is a type of magnetic force known as an electric current, a changing electric field, or a vector field around a magnet. The magnetometer compass needles and other electromagnets align in the direction of magnetic fields like the one found on Earth. Magnetic fields force all electrostatically charged particles to move in a cyclic or spiral pattern.

3. What is the line of force?

Ans. A line of force is a  suitable test particle in a given force field that follows the same path as an electric charge to move in an electric field freely. In a more general sense, lines of force will be any given force field’s lines, the density from which indicates the intensity of the field and the tangential of which, at any position, determines the direction of the magnetic field.