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The magnetic field is the region in which the influence of magnetism is felt around a magnet. A magnetic field is a tool that we use to explain how magnetic force is dispersed in the space surrounding and within magnetic objects in nature.
History of Magnetic Field
Early Stages of Development
While ancient cultures were aware of magnets and some of their capabilities, it was in 1269 when French scholar Petrus Peregrinus de Mari court used iron needles to draw out the magnetic field on the surface of a spherical magnet.
Mathematical Development
Magnetic poles attract and repel according to an inverse square rule, according to John Michell in 1750. In 1785, Charles-Augustin de Coulomb empirically confirmed this, asserting that the north and south poles cannot be separated. In 1820, three discoveries shook the foundations of magnetism. A current-carrying wire is encircled by a circular magnetic field, as Hans Christian Orsted proved.
Michael Faraday developed electromagnetic induction in 1831 when he discovered that a changing magnetic field creates a surrounding electric field, which he named Faraday’s law of induction. Lord Kelvin, then known as William Thomson, differentiated between two magnetic fields, commonly referred to as H and B, in 1850.
Maxwell’s equations, which described and linked all classical electricity and magnetism, were created and published between 1861 and 1865 by James Clerk Maxwell. In 1861, a study titled On Physical Lines of Force presented the first set of these equations.
Recent Advancements
Tesla created the first alternating current induction motor in 1887. To turn the motor, polyphase current was employed, which formed a revolving magnetic field. In May 1888, Tesla secured a patent for his electric motor. Galileo Ferraris independently explored rotating magnetic fields in 1885 and presented his findings to the Royal Academy of Sciences in Turin in a report that was published barely two months before Tesla received his patent in March 1888.
Magnetic Field Schematic Representation
A magnetic field may usually be shown in one of the following two ways:
- Magnetic field vector
- Magnetic field lines
Vector of Magnetic Field
A vector field can then be used to explain the magnetic field analytically. The vector field is composed of a grid of many different vectors. Each vector in this scenario points in the same direction as a compass and has a length that is proportional to the strength of the magnetic pull.
Lines of Magnetic Fields
Field lines are a different way of representing the information in a magnetic vector field. Magnetic field lines are made up of fictitious lines.
Magnetic Field Line Properties
- Magnetic field lines never cross.
- The density of the field lines represents the field’s intensity.
- Closed loops are always formed by magnetic field lines.
- Magnetic field lines always originate or begin at the north pole and end at the south pole.
Strength of Magnetic Field
Magnetic field strength, often known as magnetic field intensity or magnetic intensity, is a measure of how strong a magnetic field is. It’s denoted by the letter H, and defined as the proportion of MMF (MagnetoMotive Force) required to produce a given Flux Density (B) within a given material per unit length of that material. The strength of a magnetic field is measured in amperes per metre.
Tesla is the SI unit for magnetic field strength. The field intensity generating one newton of force per ampere of current per metre of the conductor is specified as one tesla (1 T).
It is given by the formula:
H=Bμ−M
Where,
- B is the magnetic flux density
- M is the magnetization
- μ is the magnetic permeability
What Induces a Magnetic Field to Exist?
When a charge moves, it creates a magnetic field. There are two primary methods for getting a charge moving and generating a meaningful magnetic field. The available alternatives are as follows:
- Magnetic field created by a current-carrying conductor
- Motion of electrons around the nuclei of atoms
A current-carrying conductor produces a magnetic field.
Let’s understand the concept of magnetic force on a current-carrying conductor:
When an electrical charge is in motion, according to Ampere, a magnetic field is formed. Consider a wire that is connected to a battery to make current flow. The magnetic field extends in lockstep with the current passing through the conductor. The magnetic field weakens as we travel away from the wire. This is defined by Ampere’s law. The magnetic field at r from a long current-carrying conductor I is given by the equation, according to the law.
B=μI2πr
Magnetic fields can be concentrated by materials having a higher permeability.
Since it is a vector quantity, the magnetic field has direction. The right-hand rule can be used to calculate conventional current flowing via a straight wire. To use this rule, imagine wrapping your right hand around the wire and pointing your thumb in the present direction. The fingers depict the magnetic field’s direction as it wraps around the wire.
The Movement of Electrons Around Atomic Nuclei
The mobility of electrons around the nuclei is what makes permanent magnets operate. Only a few elements can be turned into magnets, and some are significantly stronger than others. Some precise requirements must be followed to achieve this state.
Atoms have a large electron density that are coupled in a way which cancels out the overall magnetic field. The spin of two electrons linked in this fashion is said to be opposing. We may deduce from this that atoms with one or more unpaired electrons with the same spin are required for a material to be magnetic. Iron is a substance with four of these electrons, making it ideal for creating magnets.
Conclusion
Billions of atoms make up a little bit of the substance. Regardless of how many unpaired electrons the material contains, the total field cancels out if they are oriented randomly. At room temperature, the material must be stable enough to allow for the establishment of an overall favoured orientation. We have a permanent magnet, also known as a ferromagnet, if it is established permanently.
When exposed to an external magnetic field, some materials become sufficiently highly ordered to become magnetic. The external field aligns all of the electron spins, but once the external field is withdrawn, the alignment evaporates. These materials are referred to as paramagnetic.
