Question

Magnetic flux lines, by itself, is not very useful. You can’t see them. You can’t touch them. They can’t be detected by sensors. So, by themselves, they are not very useful. Yet, as a concept they very useful. But within a context, when they are changing in time, in the vicinity of other things (what things?) they are important. Explain where Magnetic Flux is useful, where it is important?

Answer 1

Magnetic flux is the number of magnetic field lines passing through a given surface.

Use of magnetic flux : ( Theoretical and practical )

1.It is helpful in understanding and explaining the effects of a magnetic force or a magnetic field in a particular region or on a surface.

2. It helps in visualizing a magnetic field in a given region around a magnet or a current carrying wire.

3. Magnetic flux concept is highly useful in explaining the phenomena related to changing magnetic fields. It is the foundation of electromagnetic induction

Electromagnetic induction depends on the concept of magnetic flux. Faraday's law states that " the rate of change of magnetic flux is equal to the induced emf "

Emf E = - d/dt ............ ( 1 )

Again = B . A = B A cos .......... ( 2 )

E = - d /dt ( B.A ) .......... ( 3 )

From equations ( 2 ) and ( 3 ) , we can observe that we can change the flux either by changing the magnetic field or the area by rotating the given loop. Thus we can obtain the required emf in coils and thus the current.

4. Whenever the analysis of a magnetic field due to ( or ) on a surface is complicated , it can be made easy using the concept of magnetic flux.

This is made easy by Gauss law of magnetism. It states that magnetic flux through a closed surface is zero.

5. Changing of orientation of coils relative to the magnetic field to change the flux is being utilized in electric motors and generators.

6. In generators , a coil is made to rotate in a magnetic field. This rotation changes the flux passing through the coil thus inducing a current in it.

7. In induction furnaces , Eddy currents are used to melt the objects. This Eddy currents are produced by changing the flux through a metal conductor.

8. ATM cards work on the principle of changing the magnetic flux. When an ATM card is inserted into the machine , a change in the flux linked with the wire inside helps to detect the card.

9. Security systems consists of a wire in which a flux change occurs whenever a iron object passes near it thus helping to detect any harmful objects.

Importance of Magnetic fux :

As already stated above concept of magnetic flux is important in

1. Studying the complex magnetic phenomena

2. Generation of induced electric and magnetic fields.

3. In the calculation of induced emf and induced currents in various devices which use changing magnetic fields

4. In the design of electric motors and electric generators.

5. In the design of many more modern equipment like ATM's , electric guitars , induction stoves etc that make the life of humans a lot easier.

Thus even though magnetic flux seems to be only theoretical, it has greater importance in the society that is mostly dependent on electromagnetic phenomena .