Electromagnetic Field, Electromagnetic Field Structure, Sources of Electromagnetic Fields (For CBSE, ICSE, IAS, NET, NRA 2022)

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Electromagnetic Field

  • An electromagnetic field (also EMF or EM field) is a physical field produced by the movement of electrically charged objects
  • It is one among the four fundamental forces of nature; other includes strong interaction, weak interaction, and gravitation.
Electromagnetic Field
  • It affects the change in the behavior of charged objects surrounding a particular place. It extends indefinitely throughout space and known as electromagnetic interactions.
  • It is a combination of electric field and a magnetic field and often considered as the sources of the electromagnetic field.
  • The electric field is generated by stationary charges, while the magnetic field is produced by moving charges. Lorentz Force Law and Maxwell՚s Equation explains how the interaction between currents and charges occurs with the electromagnetic field.

Electromagnetic Field Structure

The structure of electromagnetic field can be classified in two methods:

  • Continuous Structure
  • Discrete Structure.

Continuous Structure

  • Magnetic and electric fields are produced by an even motion of charged objects.
  • The oscillating charges that produce magnetic and electric fields can be observed in a continuous, smooth, and wavelike motion.
  • The energy is observed as being continuous transfer between two electromagnetic field locations.

Discrete Structure

  • Many experiments has revealed that in a particular circumstance the electromagnetic energy flows in a fixed frequency or a more harsh way in case of a photon.
  • The Planck՚s link the photon energy to its frequency. The equation is given below.


E = Photon Energy

h = Planck՚s constant

v = Frequency of Photon

Sources of Electromagnetic Fields

Natural Sources

  • The emf can see everywhere in the surrounding, but they are invisible to human eye.
  • The electric fields are produced by the electric charges that are present in the environment associated with thunderstorms.
  • While the magnetic field of the earth causes the compass needle in North-South Direction. This is used as navigation for fish and birds.

Man-Made Sources

  • Apart from the natural sources the electromagnetic field also includes the energy generated by man-made sources.
  • Few human-made electromagnetic field sources are x-rays, electricity passing through the power socket and more. It depends on the frequency radio waves and how they are associated.
  • For example, high frequency waves are used for broadcasting information through radio stations, television antennas, and mobile networks.

Difference between Electric Field and Magnetic Fields

Difference between Electric Field and Magnetic Fields
Electric fieldsMagnetic fields
Produced by voltageProduced current
Created by differences in voltage: the higher the voltage, the stronger will be the resultant fieldCreated when electric current flows: the greater the current, the stringer the magnetic field
An electric field will exist even when there is no current flowing.If a current does flow, the strength of the magnetic field will vary with the power consumption
Measured in volts per meter (v/m)Measured in gauss (G) or tesla (T) , 1 T = 10000 G
Easily, shielded (weakened) by conducting objects, such as metal, trees, and buildingsNot easily shielded (Weakened)
Strength drops off quickly as distance increases (unlike radio waves)Strength drops off quickly as distance increases (unlike radio waves)

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