Just like how the electric field surrounds the electric charge, the magnetic field refers to the area surrounding a magnet, which exerts a magnetic force due to the moving electric charges. To be specific, the magnetic field is the region surrounded by the moving charges or magnetic material within which there is a force of magnetism acting. The magnetic field lines represent the magnetic field. The symbol for denoting the magnetic field is "B" or "H."
Let us have a better understanding of this concept by considering a magnetic field surrounding a magnet. We already know the fact that a magnet attracts small pieces of iron even where they are kept at a distance apart. Therefore, just like the gravitational and electric force, the magnetic force also acts at a distance. The concept behind the force acting at a certain distance can be well-explained by understanding the term magnetic field. The magnet attracting the small pieces of iron gives rise to the magnetic field in the area or region surrounding it.
Almost every other individual across the globe is familiar with magnetic objects and has experienced that there is indeed some force acting between them. The concept of magnetic field mediates the phenomenon of magnetism. The force that one magnet exerts on some other magnet can be well-described as the interaction between one magnet with the magnetic field of the other magnet. For describing the magnetic field around a magnet, the convenient way is to draw the magnetic field lines or magnetic lines of force around its region. They are defined as the imaginary lines, which represent the direction of the magnetic field such that the tangent at any point is in the direction of the field vector at that particular point. The magnetic lines of force start at the North Pole and end at the South Pole. In the figure given below, we can observe that the magnetic field lines are diverging from the North Pole and converging at the South Pole.
Another concept that deserves adequate attention is how the magnetic field lines occur. Well, the answer is that the magnetic field lines occur whenever the electric charge is in motion. Hence, it is quite evident that if we apply more electric charges in the motion, then the strength of the magnetic field shall consequently increase. Additionally, it is essential to keep in mind that the concepts of magnetism and magnetic field are an integral part of the electromagnetic force, which is a kind of physical interaction occurring between the electrically charged particles.
SI Unit of Magnetic Field
We can define the magnetic field in many ways corresponding to the effect it has on our surroundings or environment as a result of which, we have the B-field and the H-field (magnetic field denoted by symbol B or H). B-field is a kind of magnetic field, which refers to the force it exerts on a moving charged particle. H-field is similar to B-field except for the fact that it is defined inside a material. However, there are different ways of measuring them. In the SI system, B is measured in Tesla, denoted by the symbol T and H is measured in Amperes per Meter, denoted as (A/m). A flux density of one Weber per square meter or Wb/m2 is one Tesla, where Weber (Wb) = SI unit of Magnetic flux (number of magnetic field lines passing through a given closed surface).
According to Lorentz Force Law, F(Magnetic) = qvB, where q = electric charge, v = velocity, and B = magnetic field. So, we can say that a particle carrying a charge of 1 coulomb, moving at 90 degrees (perpendicularly) through a magnetic field of 1 Tesla, and at a speed of 1 meter per second, experiences a force of magnitude 1 Newton.
We can also define Tesla (T) as:
T = V.s/m2 = N/A.m = J/A.m2 = H.A/m2 = Wb/m2 = Kg/C.s = N.s/C.m = Kg/A.s2, where V = volt, s = second, m = meter, N = newton, A = ampere, J = joule, H = henry, Wb = weber, Kg = kilogram, and C = coulomb.
Other Common Units of Magnetic Field
In the CGS system, a smaller unit of the magnetic field (B-field) is Gauss, denoted by the symbol G. The relation between Tesla and Gauss is given as 1 T = 10,000G. Furthermore, the H-field in the CGS system is measured with the help of Oersted (Oe), which is equivalent to 1 dyne per maxwell.
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