What is Electromagnetic Field ?

As we all know, a field is nothing but a physical quantity that’s assigned to every point in space. The electromagnetic field is a combination of electrical and magnetic phenomena that exist in space and it is also created by the motion of charges (electric field) which creates a magnetic field. In simple terminology electromagnetic field is a wave that transports electromagnetic energy with the speed of light. It is a scalar quantity that has only a magnitude not direction associated with it. It is a field described by classical thermodynamics. Maxwell’s law and Lorentz’s force law describe how electric charges constitute current and interact with a magnetic field. Here the important point to catch is without electromagnetic waves we can’t generate electromagnetic fields so both these terms are dependent on each other.

Electromagnetic Field

The electromagnetic field is a combination of an invisible electric field and a magnetic field of forces. It is naturally created by the earth’s magnetic field and human activities (also called EMF). It is a scalar quantity having only magnitude and not direction and it is represented by the symbol E or ε. Some Examples of EMF are smartphones, Computer Systems Transmission power lines, and so on. Electromagnetic waves are formed when an electric field comes in contact with the magnetic field. Unit of EMF is Volts per meter (V/m). It was discovered by Michael Faraday in 1831 and Joseph Henry in 1832.

The formula to calculate electromagnetic field is given by :

F = q (E + v × B)

where F is an force experienced, E is an electric field and B is an magnetic field followed by an charge (q).

Electromagnetic Field Sources

• Man-Made Sources includes X rays, any object with an charge flowing, and also mobile phone and microwave ovens, antennas, optical fiber technology.
• Natural Sources includes such as we know that earth is an big magnet as it contains combination of electrical and magnetic phenomena which is invisible to human eyes and another such natural example is thunderstorms.

Electromagnetic Waves

Electromagnetic Waves is first postulated by James clerk Maxwell and succeeded by Heinrich Hertz. It is created by oscillating electric field and magnetic field which are universally confirmed fundamental equations of electrodynamics (charges in motion). It is transverse in nature and it travels at a constant velocity of 3×108 m.s-1. It consists of sinusoidal wave where the time-varying electric field and magnetic field are perpendicular to each other and also perpendicular to the direction of propagation of waves.

Equations Used in Electromagnetic Waves

Some equations used in electromagnetic waves are –

• Gauss law
• Gauss law for magnetism
• Faradays law of electromagnetic induction
• Amperes Maxwell law

Gauss law

This law is related to the Electric Field Around a Point Charge (q). This law is known as gauss law for electricity. The total number of flux lines passing through particular surface area is equal to q/ϵ and it is represented below

Gauss law for electricity = ∫ E . d A = q ϵ

Gauss law for Magnetism

This law is known as gauss law for magnetism here the magnetic field or region across any closed surface is said to be zero, which is related to Electric Field in a Magnetic Field (B). it is represented below :

Gauss law for magnetism = ∫ B . d A = 0

Faradays Law of Electromagnetic Induction

This is one of the fundamental laws which is used to predict how a magnetic field (B) will interact with electric circuit to create an electromotive force (EMF). This phenomenon is called electromagnetic induction. it is represented below

∫ E . d l = − d/dt ( ∫ B. d A)

Amperes Maxwell Law

It states that in an electric current I or an changing magnetic flux through a surface produces circulating magnetic field around a path . Electric fields are proportional to magnetic fields.

∫ B . d l = μ ( I + d dt (ϵ ∫E. d A))

Properties of Electromagnetic Field

Electromagnetic field, a property of space caused by the motion of an electric charge. A stationary charge will produce only an electric field in the surrounding space. If the charge is moving, a magnetic field is also produced. Electric and magnetic fields are both components of an electromagnetic field.

The properties of Electromagnetic field are as follows:

• Scalar and Vector Properties
• Transverse in Nature
• Exhibits Dual Nature
• Superposition Principle
• Exhibits Wave Like Properties
• Describes Behavior of Charged Particles
• Speed of Propagation
• Characteristic Wavelength and Frequency
• Electromagnetic Spectrum

Categorization of Electromagnetic Field

The structure of electromagnetic field is categorized in two distinct structure:

• Continuous Structure
• Discrete Structure

Continuous Structure

Electric field and maThe oscillating charges that produce magnetic and electric fields can be observed in a continuous, smooth and wavelike motion. The energy is viewed as being transferred continuously between two electromagnetic field locations. Magnetic field is produced by the even motion of the object or we can say the uniform motion of the object

Discrete Structure

This shows that the electromagnetic energy flows in a fixed frequency and In Discrete Structure ,the transfer of electromagnetic energy is better described as being carried in the form of packets called “quanta” with a fixed frequency.

Planck’s relation links the photon energy ‘E’ of a photon to its frequency ‘f’ through an equation mentioned below:

E = hv

Mathematical Representation of EM Waves

Maxwell gave the basic idea about electromagnetic radiations on the other hand it is Hertz who experimentally proves and confirmed the existence of Electromagnetic waves.

As we all know that In the electromagnetic field three important factors involved and that is E is an electric field vector and B is an magnetic field vector respectively

Consider an plane has an electromagnetic wave which is travelling in Y direction is of the form :

E(y , t) = Emax cos (kx-wt+Φ)

B(y , t) = Bmax cos(kx-wt+Φ)

Here we use vector cross product of the electric field and magnetic field which is given by :

E x B

Properties of EM Waves

• EM waves are transverse in nature. it means that oscillating electric field and oscillating magnetic field in a particular plane which is perpendicular to the direction of propagation of wave.
• EM waves are non-mechanical in nature it means that they did not require any medium for propagation.
• Here the magnetic field and electric field are right angles to each other and perpendicular to the propagation of the wave.
• They travel with speed of light and it is given by 3 x 108 m.s-1.
• The product of wavelength and frequency is equal to the c (constant) which is speed of light. it can be represented by :

c= f λ

Applications of Electromagnetic Field

• Home Appliances – Kitchen appliances such as induction cookers, microwave ovens, bread toasters and electric grinders use electromagnetism for their operations. Another important application is that we all have TV, radio use loudspeakers these devices consists of electromagnet which is actually attached to the cone surrounded by the magnetic flux produced by magnets, Electric fans and other cooling systems use electric motors which is moved by the magnetic field produced by electric current.
• Medical Terminologies – Mostly Gamma rays are used for medical purposes with high frequency. EMF with frequency that range from 0 to 300 GHz can be used for therapeutic and diagnostic purposes. In MRI scans, medical appliances works based on electromagnetism can scan minute details of human body.
• Communication Systems – High frequency radio waves used for transmission of energy over long distances through electromagnetic waves. Consider an mobile phone, here the sound energy is converted into electromagnetic energy and electromagnetic waves travel forth and come back through using radio transmitters.
• Electric Trains – High speed trains uses electromagnets to develop the speed . Here the train will float due to electromagnetic suspension(EMS) and electromagnetic dimension (EDS) therefore these type of systems need large electrical power source.
• Ultraviolet Rays – It helps to learn more about space science and galaxies for astronomers because of shorter wavelengths.

Difference Between Electric Field (E) and Magnetic Field (B)

Electric Field	Magnetic Field
It is an vector quantity.	It is an vector quantity
It is perpendicular to the magnetic field (B) .	It is perpendicular to the electric field (E).
S.I unit of Electric field is Newton per meter .	S.I unit of magnetic field is (T) tesla.
To detect and measure the presence of electric field Electrometer is used .	To measure the existence of magnetic field Magnetometer is used.
It influences only electric charges.	It influences only magnetic poles.

Conclusion

These are just some of the key ideas and concepts, applications that you need to know about Electromagnetic waves and Field. It covers an essential aspect of classical physics. Numerous things or devices use or functions with electromagnetic waves. As we know that electromagnetic waves composed of photons (a particles represents quantum of light) that pass through vacuum or any medium. In this article you will not only get an idea of EM waves, but you’ll get more about how our world functions.

FAQs on Electromagnetic Fields and Waves

What is Electromagnetic spectrum?

It is the range of all type of EMF radiation or In other words it is the complete frequency distribution of electromagnetic radiation and it is divided into various parts such as visible light, infrared light, or ultraviolet radiation.

What is EMF?

It stands for Electro Motive Force which is created by Electromagnetic Induction by way of moving magnetic field around electric conductor. It is also called electric potential and denoted as ε.

State Faradays First Law of Electromagnetism?

It states that whenever a current carrying conductor is placed in a varying magnetic field, EMF is induced in it.

Mention any three applications of Ultra-Violet radiations?

• Kills bacteria.
• Water purification.
• Phototherapy.

What are the uses of radio waves and microwaves ?

• In Radio waves – Radio and Television purpose.
• In Microwave – Satellite communications.