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Magnetic Flux And Current: 9 Facts You Should Know

January 20, 2024July 12, 2022 by Keerthana Srikumar

Magnetic flux and current go hand in hand, and they have the differences. When current is induced in an area there will be magnetic flux and this magnetic flux will be opposite to that of the normal flux.

Now there will be a coil where we will induce current into it and then we can see the production of a magnetic flux. we see that when there is current induced there will automatically be an electric field and magnetic field produced inside the coil. So now when there is both magnetic and electric field there will also be flux lines.

Magnetic flux is simply the quantity which measures the amount of magnetic force that passes through a unit area per unit time. The magnetic flux is generally the number of lines which usually pass through the given unit area.

Is magnetic flux same as magnetic current?

Simplest terms, a magnetic flux is comparable with electrical current as well as a magnetization in which current plays a major role is comparable with electrical voltage.

Although there are significant distinctions, a magnetic circuit is comparable to an electrical circuit. Magnetomotive force is equivalent to electromagnetic force inside of an electrical circuit.

Every current that flows in a circuit would produce an opposing magnetic flux to one that was there before the current was produced. The induced current creates a north pole heading in the direction of said magnet’s north pole towards a conductive path. As a result, the change that brought about the current is repelled by this force.

How does magnetic flux affect current in a circuit?

An ample amount of voltage (emf) can therefore be generated into to the winding solely through magnetism. The three different elements listed below which influences the current in the circuit by partially affecting the emf across them.

Expanding the quantity of wire turns in the windings – As the multitude of transmission lines or the coils slashing across the magnetic field increases, the sum of induced electromotive force generated would be the summation of all the specific grooves of the coil; therefore, if the coil has 20 turns, there will be 70 percent extra caused emf than in a single loop of string.

Enhancing the relative movement of the coil with regards to the magnetic flux – Apart from the number of wounding, if the coil passing through the same magnetic field but with an increased velocity, the wires would interrupt the magnetic flux lines more quickly therewith producing an enhanced emf.

Strengthening the magnetic field – When the same coil is forced into a much stronger magnetic field, more magnetic flux lines would be broken and produces more emf.

How does magnetic flux relate to current?

The magnetic field becomes significantly stronger when the wire is twisted into a coil, creating a strong and static magnetic field surrounding on its own in the form of an electromagnet with a clear direction from north to south. The magnetic flux that formed around the coil was inversely proportional to the applied current running through its coils.

This dynamic magnetic flux would be enhanced if successive layers of wire were coiled together on the same loop with much the same current running across them.

As a result, a coil’s ampere spins are what decide how strong its magnetic field is. The coil’s static magnetic flux becomes stronger as more wire turns inside of it.

Does magnetic flux change with magnetic current?

Yes, the magnetic flux changes with magnetic current. In order by changing the strength of the magnetic field, the number of loops or the relative movement of the coil with the field the current changes proportionally.

E.g. When the generator is rotating around a loop or volume of loops of wire, it induces a current around the loop which in turn changes the flux at a fixed magnetic field.

Thus, the output of the generator is produced when the induced voltage produced around the loop stimulates the current to flow. The change in current with respect to the magnetic flux can be explained with Lenz law.

Lenz Law: The induced current will always flow in the direction of increasing the flux inside the loop. Incase if there is a decrease in flux produced then the current will flow in the opposite direction.

**“Currents related to magnetic fields” Image Credits: Wikimedia**

How does current change in the magnetic field?

The ferromagnetic substance is transported past the wire coil in order to follow magnetic field information. So, when the ferromagnetic substance is brought across the wire the magnetic field that is surrounding the data which enables reading is modified completely.

The object’s motion actually induces the current in the coil which in turn shifts the magnetic field. Hence proportionally the changes are brought in the magnetic field. When the speed of transportation of the ferromagnetic substance is increased the magnetic field would also be increased producing inducing emf.

magnetic flux and current — **“Magnetic Field” Image Credits: Wikimedia**

How to calculate magnetic flux from current?

A portion of the flux is evenly spread throughout the coil as it is moving. Let the magnetic flux be denoted by B and the unit is Weber (Wb). Since it is direction dependent it is a vector quantity. The magnetic flux is hence denoted by ϕB. Let n be the number of coil turns and A be the cross section of the wire, So the magnetic flux will be ΦB = n BA cosθ Wb

According to Biot-Savart law, The magnetic intensity at any place in the coil is directly proportional to the current flowing across the wire and inversely proportional to the length of the wire from that point.

Where B is the magnetic field intensity, µ0 is the permeability whose value is 4π, A is the area of the coil wounded and N represents the number of wounding. Hence the formula is given by,

B=µ0NI/ 2A

**“Magnetic field and the currents” Image Credits: Wikimedia**

Graph between magnetic flux and current

The direction of the magnetic flux is in right angles to the current induced inside the coil. We also know that when there is current there is electric field and magnetic field as well inside it.

Below given is the graph plotted between two conductors A and B, where it is between the magnetic flux and the current. When current is increased there will also be an increase in the magnetic field.

Problem:

The circular coil of radius 6 × 10-2 m and with 30 turns is carrying a current of 0.35 A. Calculate the magnetic field of the circular coil at the center.

Solution:

The radius of the circular coil = 6 × 10-2 m

Number of turns of the circular coil = 30

Current carried by the circular coil = 0.35 A

Magnetic field is given as:

B=µ0NI/ 2A

= 4π × 10-7 (30) (0.35) / 2 (2 π (6 x 10-2)

= 1.75 x 10-5 T

Conclusion

Magnetic flux is the number of line that is passing in a given unit area per unit time. Magnetic flux and current both must exist due to the production of the magnetic and the electric fields. In order to know how the magnetic field which exist we also need to know that current must be passed in the system.

Genetic Diversity In Meiosis: What, How, Causes And Detailed Facts

January 20, 2024March 20, 2022 by Sugaprabha Prasath

Genetic diversity is a concept in which the variety of characteristic features of one specific organism present on the basis of genetics like different breeds of dogs, cats or variety of rose, hibiscus flowers.

Genetic diversity in meiosis is based on 2 factors, One is the crossing over and the random arrangement or alignment of homologous pairs of chromosomes. Recombination happens and new variants of the same species emerge by the process of cell division called the meiosis. Meiosis is the only process in which a diploid cell that is “2n” becomes hapoid which is “n”.

This article completely focuses on explaining the topic Genetic diversity In meiosis in a very explicit way.

What is genetic diversity in meiosis?

In comparison with mitosis, meiosis shows or creates more genetic variation.

There are 2 factors- crossing over and random arrangement or the independent assortment.

Independent Assortment: The formation of random arrangement in chromosomes is called an independent assortment which leads to genetic variation in meiosis. This is also called random alignment or arrangement.
Crossing over: Exchange of genes among the homologous chromosomes which leads to the recombinant chromosomes which has the possibility in which the gene can have the parent cell gene.

What is the genetic diversity in meiosis in comparison with mitosis?

In comparison with mitosis, meiosis shows or creates more genetic variation.

In meiosis, four cells are produced from the parent cell and they are not genetically identical to their parent cell.
In mitosis, 2 cells are produced which are definitely identical to the parent cell.

What are Sources of genetic diversity in meiosis?

As discussed earlier, there are two sources of genetic diversity in meiosis.

The two sources of meiotic genetic diversity are the independent assortment or also called as random arrangement and the second one the crossing over process.

What are the causes of genetic diversity in meiosis?

Meiosis is a significant process in which a diploid cell (2n) becomes haploid cell (n).

Recombination is a systemic process in which new variants or to be more clear now versions of the same species cells emerge. Recombination is the major cause of genetic diversity in meiosis.

What is genetic variation in general?

Genes are the functional unit of heredity.

Genetic variation is the variety of genes or the genetic differences that take place between the same species.

Example: The parents both father and mother, have brown hair but the child has dark black hair. This is because the child has got the genes responsible for hair from one of their grandparents.
So the child has genetic variation in comparison to parents.

what chromosomes are made up of — Chromosome
Image credits- Flickr

What is Meiosis?

Meiosis is a process of cell division. It is a process in which one single parent cell produces four cells with half the number of chromosomes from which the cells that they were originated from, that is the parent cell.

So this is a significant process in which the diploid cell becomes haploid.

There are few stages involved in this process of cell division.

Prophase-I
Metaphase-I
Anaphase-I
Telophase-I and Cytokinesis
Prophase-II
Metaphase-II
Anaphase-II
Telophase-II and Cytokinesis

Meiosis diagram — Meiosis process
Image Credits- Wikimedia

Prophase-I:

The thin strand of chromatin condenses and forms compact short chromosomes which is called the chromosome condensation. Then the nuclear envelope breaking open finally leads to the process of crossing over.

Metaphase-I

These homologous pairs of chromosomes are transported to the center of the cell known as the equator region of the cell.

Anaphase-I:

Now, each homologous chromosome moves towards the opposite poles of the cells.

Telophase-I and Cytokinesis:

The chromosomes grouped in the opposite poles, the division of cytoplasm takes place.

Prophase-II:

Spindle formation takes place at this step.

Metaphase-II:

The chromosomes gather into the equator that is the middle or the center of the cell.

Anaphase-II:

The chromatids reach to the opposite poles and the centromeres division takes place.

Telophase-II and Cytokinesis:

Disappearance of spindle fibers and formation of nuclear membrane around the chromosome sets takes place.

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What Is The Magnetic Field Around A Bar Magnet: Exhaustive Facts On Various Objects

January 20, 2024December 5, 2021 by AKSHITA MAPARI

In this article, we are going to see what is the magnetic field around a bar magnet and Where is the magnetic field of a bar magnet strongest.

The magnetic field caused by the presence of the bar magnet is extreme at the edges of the poles and is very poor at the middle of the bar magnet.

What is a Bar Magnet

A magnet appearing like a bar, and hence called a bar magnet has two poles, the poles of the bar magnet are protected from demagnetizing the magnet using iron plates on both the poles.

A bar magnet is composed of ferromagnetic material that retains its magnetic properties even in the absence of an external field and hence is a permanent magnet.

On hanging freely in the air, the bar magnet aligns itself in the North-south direction. The magnetic dipoles inside the bar magnet experience the magnet force due to the Earth’s magnetic field and align in the direction of the field. Hence, a bar magnet can therefore be used to find the direction same as a compass.

Types of Bar Magnet

There are two types of the bar magnet, they are:-

1) Rectangular bar magnet: This magnet has four rectangular faces painted and two square shape poles. The edges of this bar magnet are rectangular in shape and hence the name rectangular bar magnet.

2) Cylindrical bar magnet: The edges of the magnet are circular and therefore called cylindrical bar magnets. The outer curvature of this magnet is coloured.

Where is the Magnetic Field of a Bar Magnet Strongest and Why

The magnetic field is strongest at the edges of the poles of the bar magnet.

If we take a simple example that we probably have performed as the first experiment at schools when were introduced about the magnetic field, an experiment with a bar magnet and an iron foils. The bar magnet when placed in a tray of iron foils, the iron foils are arranged around the bar magnet in well-aligned concentric circles without overlapping.

The majority of the irons are gathered near the North and the South poles of the bar magnet. This is because; the magnetic field lines are originating from the poles. The strength of the field weakens drastically as the distance from the poles widens.

Secondly, the bar magnet actually acts as a dipole, the negative and positive particles spin are aligned according to the magnetic field of the Earth. Dipoles themselves behave like a small tiny magnet. Even if we cut the bar magnet further into pieces, it will show the same behavior forming two poles of the opposite charges like a bar magnet.

The magnetic dipoles in the magnet will always align themselves as per the magnetic field. The positive and negative spins will try to align towards the poles of the bar magnet thus intensifying the strength of the magnetic fields at the poles.

Where is the Magnetic Field of a Bar Magnet Weakest

If we look into the same experiment as mentioned above; we shall see, there are hardly any iron foils attached on the middle portion of the bar magnet, nor you will find any field lines originating from this part of the magnet and are almost parallel to the length of the bar magnet.

Also, it is been observed that the magnetic field lines which are running parallel to the length of the bar magnet are separated from each other making a gap that widens every loop. While at the poles, the magnetic lines are more densely without forming any gap.

The magnetic field strength of the bar magnet through intense at the poles will start faltering as the distance between the poles increases.

The tiny dipoles inside the bar magnet always align themselves in the direction of the Earth’s magnetic field, hence the spins are oriented towards each pole.

The parallel aligned dipoles show both attraction and repulsion thus neutralizing the effect of the magnetization; there is a presence of a magnetic field but comprises weaker strength of the field. In consequence, diminishing the magnetic field at halfway from the poles of the bar magnet.

Is a Bar Magnet Surrounded by a Magnetic Field

The dipoles inside the ferromagnetic material of what the bar magnet is comprising of, possesses the magnetic dipole moments which are responsible for the generation of a magnetic field of a bar magnet. Being a permanent magnet, it will attract ferromagnetic materials towards it, while showing some force of attraction or repulsion on other magnetizing material when placed near the bar magnet and not too far.

The magnetic force around the bar magnet will act only when the substance is placed in its field. Outside the magnetic field of the bar magnet, evidently, the strength of the field is zero as there are no magnetic flux lines flowing in this region.

Being magnet will show some forces of attraction and repulsion in an area surrounded by it, this implies that the magnetic field does occur around the magnet, which is represented as a magnetic flux oriented in concentric circles, beyond this range of magnetic field; no effect of the magnet is observed.

How to Draw Magnetic Field Lines Around a Bar Magnet

The magnetic field lines are represented as the flux lines. These flux lines form concentric closed loops. The magnetic field produced by the bar magnet is represented by flux lines that are originating from one pole and terminate into another pole of the bar magnet.

Hence, the magnetic field lines can be drawn originating from the North Pole and entering in the South pole forming close loops, and these loops are separated from one another at a certain distance while running parallel to the length of the bar magnet and this gap widens for every loop, on the contrary, the magnetic lines are drawn dense at the poles.

No magnetic field lines should touch the middle section of the bar magnet as the magnetic field is negligible in this area and has a weak force of attraction or repulsion.

What is the Direction of Magnetic Field Lines Outside a Bar Magnet

what is the magnetic field around a bar magnet — Magnetic field direction; Image credit: teachoo

The magnetic field of the bar magnet is due to the presence of the dipole. The positive and the negative charges of a particle separated by a small distance due to some external field applied is called a dipole. These dipoles are line-up in accordance with the magnetic field. Hence, in absence of a magnetic field, the dipoles inside the bar magnet are positioned as per the Earth’s magnetic field. This orientation of the dipoles inside the bar magnet is then responsible for the direction of the magnetic field lines generating outside the bar magnet.

The dipoles are aligned parallelly in the direction from the South Pole to the North and hence the direction of the magnetic field lines outside a bar magnet are arising from the North pole to the South.

Is the Magnetic Field Same all Around a Bar Magnet

The magnetic field depends upon the strength and density of the magnetic flux lines and varies with respect to the distance from the poles. The intensity of the magnetic field is directly proportional to the magnetic flux density. The flux density varies with distance.

The magnetic field produced by the bar magnet is at a peak near the edges of the poles. The weak force of attraction and repulsion is experienced at the middle part of the bar magnet.

The reason why I am considering both attraction and repulsion in the middle portion of the bar magnet is due to the fact that the dipoles are arranged across the length of the bar magnet are parallel to the magnetic flux lines in the region outside the magnet, the dipole itself behaves like a tiny magnet.

The parallelly aligned dipoles show the force of attraction as well as repulsion from two different ends of the dipole depending upon the orientation of the spin of the charge. This results in neutralizing the effects of pulling and pushing away and weakens the magnetic field strength.

Thus the magnetic field strength is highest at the edges of the poles of the magnet. The strength decreases as the distance from the poles across the length of the bar magnet increases. The same is the effect around the bar magnet. As the distance from the magnetic poles increases the strength of the field will also decrease as we go far from the poles.

Magnetic Force Imposed by the Bar Magnet on Various Objects

The bar magnet will show the force of attraction when the ferromagnetic materials like objects made up of iron, steel, or an alloy of irons are brought in closer contact with the magnet.

Whereas, it will show repulsive forces when comes in contact with the substances having diamagnetic characteristics; for example, mercury, water; and will experience the weak force of attraction with objects like aluminum, tungsten, etc. which are paramagnetic substances.

Frequently Asked Questions

If the bar magnet of length 10cms kept on a table experience the magnetic strength 30 cms away from the magnet, then calculate the magnetic field strength of the bar magnet. The horizontal component of the Earth field is 0.34G.

Given:-

Horizontal component of the Earth

B_H=0.34G=0.34*10^-4

2l= 10cms; => l=5cm=0.05m

t=30cms = 0.30m

Neutral point is obtained on the axial line.

B_axial=B_H

[

[0.34*10³*(0.0875)²]/(2*0.30)

=4.34Am²

Hence the strength of the magnetic poles of the bar magnet is

m=M/2I=4.34/10=0.434Am

What are the different uses of bar magnets?

A bar magnet is used for various purposes may be industrial, electronics, chemical industries, laboratories, etc.

The bar magnet is used to separate magnetic substances from the heap of mixtures, for stirring the chemical mixture to facilitate the movement of the magnetic substance, in electronic devices like TV, microphones, mobiles, etc.; it is used as a small chip in the electronic devices.

Why does bar magnet have the North Pole and the South Pole?

When the bar magnet is suspended in the air, it will continuously show harmonic motion until it gets aligned in the direction of the Earth’s magnetic field.

Due to the separation of charges inside the magnet, one end of the bar magnet becomes more positive and the other is more negative. The magnetic dipoles inside the bar magnet experience the Earth’s magnetic force and are aligned with respect to the Earth’s magnetic field. The magnet has two poles same as the Earth, and in a free suspended position in the air, it will align with respect to the Earth’s magnetic field that is in the north-south direction. Hence, the names the North and the South pole to two different poles of a bar magnet.

Does the magnet work in space?

Yes. The magnet can be used in space even in the absence of an atmosphere.

As the magnetizing dipole field inside the magnet is permanent and zero work is required to build the magnetic field around the magnet, it will definitely work in space as well.

Read more about Magnetic Field Lines Around A Magnet.

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Magnetic Field Vs Magnetic Field Strength: Different Aspects and Facts

January 20, 2024November 29, 2021 by AKSHITA MAPARI

In this article, we are going to see the difference between the magnetic field and the magnetic field strength, some features, and facts.

A magnetic field is set up due to the motion of the charged particles and the captivation force is exerted in this region; magnetic field strength only intensifies this impact by increasing the magnetic flux density per unit length.

Magnetic Field Vs Magnetic Field Strength

Magnetic Field	Magnetic Field Strength
The field produced around the magnetic material due to the motion of the charged particle is known as a magnetic field.	Force experienced per unit length of a conductor for the magnetic flux to penetrate through the conductor is called magnetic field strength.
The magnetic field is stable around the magnet.	Magnetic field strength varies with distance.
Magnetic field depends on the velocity of the particle, external field, and the charge of the particle.	Magnetic field strength depends upon the magnetic flux, dipole moment, magnetic susceptibility, permeability, magnetization, and the number of charged particles.
The magnetic field is a vector quantity that has both magnitude and direction	Magnetic field strength is a scalar quantity that has only the magnitude and no direction
SI unit of the magnetic field is Tesla	SI unit of magnetic field strength is Amperes per meter
CGS unit of the magnetic field is Gauss	CGS unit of magnetic field strength is Oersted

Let us closely understand the concept of the magnetic field and the intensity of the magnetic field.

In presence of the electric field, the charged particles are in a mobile state which produces a magnetic field. In the magnetic field region, the force perpendicular to the speed of the particle is emanated. In contrast, the magnetic field strength is a pressure experienced in that area relying upon the magnetic flux passing via a unit length of the material.

The magnetic field can be interpreted as field lines whereas magnetic field strength is a density of field lines crossing per unit cross-sectional area.

Let us don’t forget an easy instance of a bar magnet positioned in a tray of iron foils. We see that the iron foils are impeccably aligned around the bar magnet forming the closed loops.

Magnetic Field Vs Magnetic Field Strength — Traces of the alignment of iron foils around the bar magnet,
Image credits: comnewsscience

The concentric loops encircling the bar magnet move from the North Pole to the South Pole of the bar magnet, that means one pole is attractive and the alternative is repulsive. But, the direction of the flux flowing inside the bar magnet is aligned in the opposite direction. The magnetic field lines form the closed loops and never intersects. However, if overlapped, the path of the magnetic field isn’t unique.

The region surrounding a bar magnet in which this magnetic effect is observed is a magnetic field region. You will notice that more number of iron foils are attracted toward the magnet in the area circumjacent it, while the density of the field lines decreases as a gap between the magnet and a point of consideration increases. That is the strength of the magnetic field diminishes as we go away from the magnet, however, the magnetic field is stable.

Magnetic Moment and the Direction of a Magnetic Field

When the material having magnetic susceptibility greater than zero is placed in the electric field, the magnetic dipoles try to align themselves in the direction of the field. Due to the motion of dipoles, the magnetic field is installed in the material. The spin and orbital angular instigation of the electron and protons will decide the direction of the magnetic field.

During this alignment, there is a change in the concentration of positive and negative charge carriers per unit volume of the material. The charged carriers are aligned in the direction of the field forming the colonies. The more the number of the charged debris aligned in accordance with the magnetic field strength adds to the magnetization of the material.

The strength of the magnetic field is the force required for the magnetic flux to penetrate through the cross-sectional area of the material making it more magnetized. Hence the magnetic field strength primarily depends upon the magnetic field produced due to the motion of charged debris and the electric field implemented to the conductor and the magnetic flux density.

Magnetic field and Intensity in free space and solid state

In free space, the magnetic field is linearly dependent on the intensity of the field, given by the relation:

B=μ₀H

where B is the magnetic field,

m is a permeability of free space and

H is a magnetic field strength.

The material is said to be more permeable if more number of magnetic fluxes are penetrating through the material. In the magnetic solid, the same is given by the product of permeability and the sum of the intensity of the field and magnetization of the material.

B=μ₀(H+M)

B=μ₀H[1+(M/H)]

Where is a susceptibility.

The total magnetic moment induced per unit volume of a material is known as susceptibility and is inversely proportional to the strength of the magnetic field.

Motion of a Particle in a Magnetic Field

For a charged particle in an electric field, experiences both electric and magnetic forces, which is known an electromagnetic effect. It is formulated as:

Since the motion of the particle is perpendicular to the direction of the magnetic field applied, the force due to the magnetic field acts as a centripetal force on the particle as the force always acts towards the centre and produces circular motion perpendicular to the field.

In a uniform magnetic field, this circular motion remains unaffected thereby moving in a helical motion.

mv²/r=qvB

B=mv/qr=p/qr

The above solution indicates that the magnetic field is directly proportional to the momentum of the particle and inversely proportional to its charge and a radius of a helix.

Scalar and Vector Quantities

The magnetic field is a vector quantity that has both magnitude and direction while the magnetic field strength is a scalar quantity that has only the magnitude and no direction.

The sum of the resultant forces experienced by the particles in the presence of a magnetic field conclusive the strength of the magnetic field. The magnitude of the field is derived by the number of flux lines passing through per unit area.

Unit of Magnetic field and Magnetic Field Strength

The magnetic field is measured in Tesla, named after the well-known scientist Nikola Tesla, and the CGS unit is Gauss. One Tesla is given as N/m.A, that is, the force required for a charged particle to cross a unit length per ampere; which is the same as the magnetic flux.

The intensity of the magnetic field is current flowing per unit length of the conductor and is measured in terms of Oersted which is also represented as Ampere per meter.

Frequently Asked Questions

What is the reason behind the formation of a magnetic field of the Earth?

The magnetic field of the Earth prevents the ionized debris approaching from the Sun to enter the Earth’s atmosphere imparting a shield, thus guarding the atmosphere and existence on our planet.

The Earth’s core composes of the majority of Iron (Fe) which is ferromagnetic. As the molten lava is denser than the plates floating on the asthenosphere, the molten lava composed of Iron and nickel penetrates towards the core of the Earth. Due to the glide of molten iron, the convection current is generated that produces a magnetic field.

What is the range of magnetic field produced in a Magnetic Resonance Imaging (MRI) machine?

Magnetic resonance imaging machines are widely used in the hospital to take pictures of the anatomy of organs in the human body to take precise details.

The magnetic field produced by an MRI machine is in a range of 0.5 Tesla to 2.0 Tesla i.e. 5000 Gauss – 20,000 Gauss; whereas the value of the Earth’s magnetic field is just 0.5 Gauss.

Does the magnetic field of the Earth change frequently?

By studying the rock samples and using the radiometric dating techniques, it is viable to determine and calculate the magnetic field strength and the direction of the field of the Earth varied even for the past millions of years ago.

Yes, the magnetic field strength of the Earth changes frequently as the geo-tectonic activities are predominant and the oceanic crust forming alongside the mid-oceanic ridge indicates the imprints of the magnetic field during that precise time on the rock. The motion of the plates on molten magma gives the idea of the strength of the magnetic field.

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