# Magnetic Lines of Force for IIT JEE

## Magnetic Flux

The magnetic line of force is a vital concept of fundamental physics. Generally, the force is a power to change the position of the particular object from its original particular region. The object position movement / change are varied based on the variations in the input force. Our living Earth contains a wide range of variety of objects. It contains living organisms, non-living organisms & both large particles & tiny particles present in the nature. Generally, some kind of force always acts on every matter. Based on the properties of matter, the force acting on the object else the force acting on the matter also varies accordingly. One fine example of that is the gravitational force which acts on the earth. It is a huge force to get back each and every matter in its original particular region by pulling them back.

Similarly like the gravitational force, some kind of force acts on the magnetic region or surface. The magnetic field is known as magnetic line of force. Generally, a magnet contains two opposite poles: one is North Pole and other one is South Pole. Magnetite is a naturally occurring rock that is a magnet. Magnetism can be naturally present in an object or the object may be externally magnetized by various methods. Magnets can be permanent type or temporary type. After being magnetized, a permanent magnet retains the properties of magnetism indefinitely. Incise of temporary magnet is a magnet made of soft iron; it is usually easy to magnetize on comparing with the permanent magnet. But, temporary magnets lose most of their properties of magnetism when the magnetizing source is discontinued. Permanent magnets are always more difficult to magnetize, but they remain magnetized. In that, the acting force, that is, the magnetic line of force is defined as an an imaginary line representing the magnetic field direction like that the tangent at any point is the particular direction of the field vector at that point. For, the better understanding of magnetic line of force we need to know about the line of force, magnetic flux &magnetic field.

Line of force

Line of force, it is particular line/ path followed by an electric chargeÂ it can be easily move in anÂ electric field,Â else a mass free to move in an earth gravitational field, or generally any appropriate test particle in a given force field. The line force is always handled with the vector field,Â VÂ = âˆ’grad Ï•, and also in addition a potential Ï• always travels normally to the equipotential region of surfaces, the changes in particular region of its traveling direction will be represented with the help of continuous lines drawn similar to that. The line & particular force acting on it is known as the line of force.

Magnetic Flux

Next, the magnetic flux is known as the overall magnetic induction crossing a region of surface, equal to the integral of the component of magnetic induction, perpendicular to the region of surface over the region of surface. TheÂ magnetic flux through a region of surface is the region of surfaceÂ integralÂ of the normal component of theÂ magnetic fieldÂ BÂ crosses through that region of surface. TheÂ SIÂ unitÂ of magnetic flux is theÂ weberÂ (Wb) and its CGSÂ unit is theÂ Maxwell. Magnetic flux is usually measured by the device named as the flux meter, which contains measuring coils andÂ electronics that calculates the change in voltageÂ in the measuring coils to evaluate the magnetic flux.

The magnetic flux can also be described with the simple concept based on the region of surface itâ€™s passing through. The magnetic interaction is explained in terms of a one field thatâ€™s called as vector field. Here, point in a particular region and time is associated with a vector that calculates what the force for moving a charge would experience at that point. This is called Lorentz force. The magnetic flux through some region of surface is proportional to the number of field lines passing through that region of surface (in some observations, the flux may be defined to be specifically the number of field lines crossing through that region of surface; but technically misleading, this distinction is not important). Note that the magnetic flux is theÂ netÂ number of field lines passing through that region of surface; that is, the total of field lines passing through in one direction minus the total of field lines passing through in the other direction.

Based, on these parameters it is easy to understand the magnetic flux by its traveling region of surfacein open& close.
For the closed region of surface, itâ€™s calculated as:

Gauss's law for magnetism, which is one of the fourÂ Maxwell's equations, states that the total magnetic flux through aÂ closed region of surfaceÂ is equal to zero. (A "closed region of surface" is a region of surface that completely encloses a volume(s) with no holes.) This law is a consequence of the empirical observation that magnetic monopolesÂ have never been found.
For the open region of surface, itâ€™s calculated as:

One of the important quantities in electro magnetism is that the magnetic flux through aÂ closed region of surfaceÂ is always zero, however, the value of magnetic flux through anÂ open region of surfaceÂ need not be zero.

And, finally aÂ magnetic fieldÂ is aÂ vector fieldÂ that represents the magnetic influence of electric charges in relative motion and also magnetized objects. Magnetic fields are observed in a wide variety of size scales, from each and every subatomic particle to galaxies. In everyday life, the effects of magnetic fields are seen inÂ permanent magnets. The permanent magnets pull onÂ magnetic objects and attract or repel other magnets. They are created by magnetized object and by movingÂ electric chargesÂ are also called as electric currents such as those used inÂ electromagnets. Magnetic fields induced forces on nearby mobile electrical charges and torques on nearby magnets. In addition, a magnetic field that varies with location induces a force on an object is called as magnetic objects. Both the strength and direction of a magnetic field varies with location and it is an example of aÂ vector field.

The word â€˜magnetic field' is used for two things but the closely related fields are denoted by the symbolsÂ BÂ andÂ H. In theÂ SI units,Â H, magnetic field strength, is measured in the SI base units ofÂ ampereÂ perÂ meter whereas B, magnetic fluxes density, is measured inÂ TeslaÂ ,Â which is similar to newtonÂ per meter per ampere.Â HÂ andÂ B differ in how they account for magnetization. In aÂ vacuum surface,Â BÂ andÂ HÂ are the same aside from units; but in a magnetized object,Â B andÂ HÂ are always found to differ by theÂ magnetizationÂ MÂ of the object at that point in the object.

The magnetic field is usually produced by movingÂ the electric chargesÂ and the intrinsicÂ magnetic momentsÂ ofÂ elementary particlesÂ  related with a fundamentalÂ property is widely known as the quantum property. Both the universal fields magnetic fields andÂ electric fieldsÂ are interrelated, and both are sub-divisions of theÂ electromagnetic force which is one of the fourÂ fundamental forcesÂ of nature.

The magnetic line of force is an imaginary line. It is available around the magnetic field in a particular line of axis. Generally, it is a line that we have matched out around the magnet and is called asÂ magnetic lines of force; indicated by the region in which the force of the magnet can be found. This region is called theÂ magnetic field. If any iron material is kept near a magnet, but it is not within the field of magnet, the object will be unable to attract towards the direction of magnet. This is the pattern that these lines of force tells us about the characteristics of the forces caused by the magnet. The magnetic lines of force, or flux, leave the North Pole and enter into the South Pole.

As already discussed, gravitational force is acting on the earth region of surface to pull the objects towards it and to pull them back to its original particular region. Same attraction occurs in magnet also. Hence, we can consider earth as a magnet since the earth is a huge magnet with a magnetic north and south pole, In the earth, the lines of magnetic force around is look like there is a huge vertical bar magnet which runs through the centre region of the earth.

As, in these modern days this magnetic line of force plays a very important role in various applications such as the following:

1) Computers and Electronics
2) Electric Power and Other Industries
3) Health and Medicine
4) Medical devices
5) Wide range of home appliances.

For the improvement in the technology employed in the electronic appliances, magnetic lines of force have played a significant role in their evolution.