An external force felt by one particle because of the other particle is the basic concept behind the study of fields. It can also be defined as," influence or presence felt by one particle because of the other." Though there are many theories and explanations built across the concept of fields. In this article, we will discuss two fields which have helped physicists to understand the concept behind the light. We are further going to discuss Electric Field and Magnetic Field in detail.
Electric field vs. Magnetic Field
The main difference between the Electric field and the magnetic field is what type of particle we are considering. If we are considering an electrically charged particle then it will create an electric field. Whereas if we consider a permanent magnetic substance (or a magnet) or a moving electrically charged particle (taken from electromagnetic theory) creates a magnetic field. Though as we get into the deep analogy of both fields. We understand that both hold a distinct significance in science. The concept of Magnetic fields is used to understand Earth’s magnetosphere. And whatever electrical appliances we use in our daily life are based on the concept of the Electric field.
Difference between an Electric field and a Magnetic field in tabular form
|Parameters of comparison||Electric field||Magnetic field|
|Definition||An electric field is a region around a charge where another charge experiences an electric force.||A region where magnetic material experiences magnetic force is known as the magnetic field.|
|Source||It is created around an electric charge.||It is created around moving charges or magnets.|
|Units||The unit is volt/metre or Newton/coulomb.||The unit is Tesla or Newton-second or Coulomb-Metre.|
|Symbol||It is denoted by E.||It is denoted by B.|
|Measuring Instrument||It is measured by Electrometer.||It is measured by Magnetometer.|
|Electromagnetic field||In an electromagnetic condition, the electric field is perpendicular to the magnetic field.||In an electromagnetic condition, the magnetic field is perpendicular to the electric field.|
|Work||An electric field can perform work as speed and direction change.||Magnetic Field does not perform work as speed is constant.|
|Originate from||The electric field induces from the positive charge and terminates on the negative charge. Positive charges produce outward-pointing lines and negative charges produce inward-pointing lines.||The magnetic field is generated at the North Pole and terminates at the south pole.|
|Closed loop||When electric field lines originate from the electric field, it does not form a closed loop.||When magnetic field lines originate from the magnetic field, it forms a closed loop.|
|Strength||The strength of an electric field is given by the magnitude of the charge and distance from the charge. An expression is given by Gauss law, i.e., E=KQr2||The strength of a magnetic field is given by the current and distance from the current flowing in a wire. The expression is: B=μ0I2πr|
|Motion||It can cause stationary charges to move.||It can make a moving charge experience a force.|
|Applications||The application of electric fields can be seen in motors, transformers, and capacitors.||The application of magnetic fields can be seen in Generators and MRI machines.|
|Interaction with light||It shows interaction with light through the phenomena of polarization. Polarisation causes an electric field of a light wave to oscillate.||It does not show interaction polarization. But they can affect the direction of light.|
What is the first question that arises in your mind, when you hear about the physical field?
A physical field or field is created by some quantity, generally charged particles, or moving charge particles and it exerts a force on another particle when it comes inside the field.
So, the Electric field is one type of physical field. And it has many applications in multiple areas of physics and the use of electric field are exploited in electrical technology. In atomic theory, the atomic nucleus builds an electric field, which exerts an attractive force towards electrons and holds them together. Fields defined in this manner are sometimes called force fields.
An electric field is a field that surrounds electrically charged particles and exerts either an attractive or a repelling force on other charged particles in the field. It generally arises from electric charges. It is generally a vector field that associates with each point in space.
An electric field is also defined as the electrostatic force per unit of charge exerted on a test charge at rest at that point.
The SI unit of the electric field is Newton per Coulomb (N/C) or Volts per metre (V/m).
If you analyse the electric field then it is gravitational in some manner, where we deal with two masses. And the similarity is the relation of both fields with distance is the same.
The relation between distance and charges is given by Coulomb's Law.
The law states that the stationary charges have an electric field which varies with the source charge and varies inversely to the square of the distance between two charges (source charge and another charge)
Electric field lines
Many theories have been given on the electric field lines. Generally, electric field lines are visualised to be the lines that have the same direction as the fields. The concept was given by a famous scientist named Michael Faraday.
This illustration is famous as it gives a rough estimation of understanding the measure of field strength. If the density of lines is more, then the field strength will also be more. This theory also says that field lines originate from a positive charge and terminate at the negative. It says that good conductors have field lines at right angles. The most important property of field lines is that they never cross each other.
Mathematics in the Electric field
The expression for the electric field was given by Coulomb’s law and Gauss’s law. Both are given on the assumption that the charge is stationary at a given point in space.
Coulomb’s law explanation has already been stated; therefore, the expression is:
This is the electric field at x1 due to charge q2. The above expression gives the electric field equation in vector form. The formula gives the magnitude and direction of the electric field at any point x1in space.
One more relation stated by Coulomb, i.e.,
The above expression gives the coulomb force F on a charge of magnitude qis equal to the product of charge and electric field.
The superposition principle states that the Total electric field applied by a number of charges is equal to the vector sum of electric fields of individual charges. The expression:
= 14π∈0q1(x1-x)2r1+14π∈0q2(x2-x)2r2+ ………………
Gauss Law says that the total flux involved in a closed surface is given by 1∈ times the charge.
The expression for Gauss’s law is:
It explains the electric field for electric charge distribution on a closed surface.
Uniform fields are a concept where the electric field will remain the same at all points. We can find that by keeping two conducting plates parallel to each other and maintaining a voltage. The expression for the magnitude of the electric field in the case of uniform fields is:
Where âˆ†V is the potential difference and d is the separation between the two conducting plates. The negative sign indicates that both charges are either positive or negative or simply unidirectional in nature. The like charges will create a repelling effect and in turn increases the potential difference.
Everyone must have seen magnets in their childhood and played with them. Most of us found it very interesting and shocking. And questions how two magnets are attracting each other.
They get attracted because of the magnetic field. This field attracts other point electric charges and currents. A force is experienced by a moving charge perpendicular to the velocity and magnetic field.
There are three effects seen due to the non-uniform magnetic field, those are-
- Para magnetism- It is a phenomenon faced by unpaired electrons when a non-uniform magnetic field is applied. These unpaired electrons align in the direction of the field, giving a net magnetic moment. Though, this phenomenon is temporary. Once the field is removed the electrons get backs to normal. Examples of paramagnetic materials are Aluminium, platinum, and oxygen.
- Diamagnetism- It is a phenomenon faced by paired electrons when a non-uniform magnetic field is applied. Magnetic dipoles of paired electrons align, so that it repels by the magnetic field. Though this cause is weak when compared with other effects. Examples of Diamagnetism are gold, silver, and copper.
- Antiferromagnetism- In this type of magnetism, adjacent magnetism moments are opposite, resulting in the net magnetic moment being zero. But when a non-uniform magnetic field is applied, the orientation reverses, which results in small amounts of magnetic moment. Examples of Antiferromagnetism are Iron oxide, nickel oxide and manganese oxide.
In summary, the magnetic field depends upon the electronic structure and orientation of the magnetic moment.
Magnetic fields are created by electric currents as used in electromagnets. These fields surround magnetised materials and whichever material comes inside; it will provide force to the material.
Electromagnetics says that the term "magnetic field" is used for two different terms, i.e., denoted by B ad H. B gives the magnetic field density. Whereas H gives the magnetic field strength. Both B and H are related to each other by a formula:
Magnetic fields derive intrinsic magnetic moments of elementary particles associated with the spin of the particle (quantum property).
The mathematics involved in the Magnetic Field
Magnetic fields are a quantity defined for moving charges, where the quantity is motion dependent. The force's component is perpendicular to the speed and direction of charged particles. Together the fields are defined by Lorentz force law, where this force is perpendicular to the motion of charge and force it experiences.
Magnetic force=q(v×B)……... (In vector form)
=q.v.Bsinθ …….. (in scalar form)
Electric field= q.E
Comprising the above two forces gives us Lorentz force,
Lorentz force (F)= q.E + q.v.Bsinθ
We can also define a magnetic torque based on magnetic dipole:
Magnetic torque= m×B= m.Bsinθ
Difference between Magnetic field and Electric Field in points
- An electric field is a region of force defined by a charged particle, which is stationary in nature. It exerts a force on other stationary objects. It is defined by force per unit charge. Whereas, a magnetic field is also a region of force defined around a moving charged particle. It exerts a force on other charged moving objects.
- The electric field points towards the electric field when a positive test charge is present. To be precise, an electric field is radial, i.e., the direction of it goes away from the positive charge and towards the negative charge. Whereas the direction of a magnetic field is given Fleming's right-hand rule, which states that thumbs give the particle's motion, fingers give the field and palm gives the force developed.
- An electric field encounters the light and has the capability to deflect the direction of light. And this is the reason for seeing multiple phenomena like reflection and refraction. Whereas magnetic field does not interact with the light directly, they first induce with the electric field and then interact with the light. This principle is known as electromagnetic theory. This is the basis for electric generators and transformers.
- In the case of an electric field, the force experienced by any charged particle is given by F=qE, where F is the force, q is the charge and E is the electric field. Whereas the magnetic field force experienced by any moving charge particle is given by F= q(v×B), where F is the magnetic force, q is the charge of the moving particle, v is the velocity of the particle, and B is the magnetic field.
It is very clear from the above explanation that both electric fields and magnetic fields are important from the perspective of studying charges. Though both fields also have many uses in our life. Like magnetic field is used in Magnetic Resource Imaging (MRI), Compasses, and so on. An electric field is used in capacitors, electric power transmission, and so on. In electric motors, the principle of both fields is used. Together it forms an electromagnetic field.
- Electric field - Wikipedia
- Magnetic field - Wikipedia
- Difference between Electric Field and Magnetic Field - GeeksforGeeks
- Electric and magnetic fields (article) | Khan Academy