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Magnetic Fields Overview : Characteristics – Facts

Jul 16, 2022


Magnetism is a natural phenomenon created by the movement of electric charges. These movements are often nano-small and take place inside a compound called magnets. Other magnets can be drawn to or repelled by magnets or by the magnetic fields produced by the movement of electric charges, which can also alter the mobility of various other charged particles.

According to the HyperPhysics website of Georgia State University, the force exerted by magnetic field lines on particles is known as the Lorentz force. An electrostatically charged particle in a magnetic field experiences forces based on the size of the charge, the particle’s velocity, and its field strength. The distinctive characteristic of the Lorentz force is that it makes particles travel in the right direction (angle) to their initial motion.

Did You Know?Some substances, like iron, are classified as permanent magnets because they can support a magnetic field that lasts forever. These are the kind of magnets that are most frequently found in daily life. When placed inside stronger, greater magnetic fields, some materials can temporarily lose their magnetic properties, such as nickel, iron, and cobalt.

Magnetic Field Lines 

Field lines are an alternative technique to depict the data in a magnetic vector field, its lines are hypothetical.

This field can be represented visually using magnetic field lines. They explain how a north monopole’s magnetic force behaves at each location.


The lines’ density reveals how large the field is. For example, magnetisation is more intense and dense near a magnet’s poles, but it starts weakening, and the lines become less thick as a person walks away from the poles.

Characteristics of magnetic field lines:

  • These lines never intersect one another.
  • The field lines’ density indicates the field’s strength.
  • The field lines form closed paths at all times.
  • These field lines usually originate from or begin at the north pole and end there.

Magnetic Field Strength

A magnetic field strength, also known as magnetic field intensity, can be defined as the ratio of MMF needed to produce a specific flux density inside a particular material per unit length of that material. One of the most fundamental ways to gauge its strength is to utilise a physical quantity known as magnetic field strength. This is measured in amperes per metre, or A/m.

Magnetic field strength is one of two ways of expressing the intensity of the magnetic field. Theoretically, there is a difference between magnetic flux density B, calculated in Newton-metres per ampere (Nm/A), also known as teslas (T) and magnetic field strength H, calculated in amperes per metre (A/m).


The field lines represent the magnetic field. The magnetic field strength is directly related to the density of the magnetic field lines. The magnetic flux (energy flow) refers to the total magnetic field lines in a given space. The tesla metre squared (T.m2 also known as weber, represented by “Wb”). The earlier units, the maxwell (equal to 10-8 Wb) and gauss (equal to 10-4 T), for magnetic flux density and magnetic flux, respectively, are no longer used and hardly observed.

The magnetic flux density decreases with the increased distance from a straight line connecting two magnetic poles or a straight current-carrying wire. The magnetic flux density is directly related to the current in amperes at a certain place near a current-carrying wire. The “magnetic force” acting on a ferromagnetic object, such as a piece of iron, is directly inversely related to the variation of the magnetic field strength where another object is placed.


Magnetic Field Strength Formula

A magnetic field strength refers to the force that a unit north pole of one-weber strength encounters at a specific location in the magnetic fields. 

The magnetic field strength formula can be derived as follows:


B = μ0I / 2πr



B = the magnetic field strength (Tesla, T)

μ0 = conductivity of free field, which is, 4μ × 10−7 T . m / A

I = intensity of electric current ( Amperes, A)

r = distance (m)

Additionally, there is a crucial connection below,

H = B / μm

H = B / μ0 – M

B can use this specific form to express its relationship.

B = μ0 (H+M)

Amperes/metres would be the same for H and M. Analysts occasionally refer to the magnetic induction or the magnetic flux density to further separate B from H. The magnetisation of the object is also the number M in these connections.

Another commonly used expression for the connection between B and H is

B = μmH


μ = μm = Kmμ0

In this case, μ0 represents the conductivity of space. Km stands for the material’s conductivity. Additionally, Km = 1 if the material does not produce any magnetisation in response to the outer magnetic fields. The magnetic susceptibility, also known as the magnetic quantity, explains the variations in the relative conductivity from one another. 

Magnetic susceptibility χm = Km – 1

It is possible to extract the unit for magnetic field strength, which is H, from its relationship to the magnetic field B.

 B = μH. 

Additionally, N / A2 is the unit of magnetic conductivity. Consequently, the magnetic field strength formula is measured in:

T(N / A2) = (N / Am) / (N / A2) = A / m

Did You Know?The oersted is another obsolescent unit for measuring magnetic field strength; 1 A/m equals 0.01257 oersteds.

Earth’s Magnetic Field

The earth’s magnetic field is generated by the electric currents high above the earth’s surface and embedded deep inside the planet. The field encounters the plasma flowing in the solar wind as it travels deep into space. It is compressed on the planet’s dayside and stretched into a long tail on its nightside due to the solar wind’s motion around it.

By dispersing solar wind’s high-energy particles, the geomagnetic field protects the earth’s surface. Massive quantities of plasma and energy from the Sun are injected into the earth’s stratosphere during magnetic storms, impacting satellites, radio communication, power grid, and auroral displays.

It has a direction and a magnitude (size). Groupings of elements or components can explain it. The graphic illustrates the most frequently mentioned elements in geomagnetism: H, F, X, Z, Y, Z, D, and I.

The direction of the geomagnetic field’s lateral (horizontal) component serves as the magnetic north’s definition, where a compass needle points (H). The angle between magnetic true north and north is known as the geomagnetic declination (D), also known as variation.

Curiously Enough:The planet earth is a powerful magnet. According to NASA, the planet’s magnetic field is generated by the flow of electric current inside its molten metallic core. The small magnetic needle in a barometer is mounted so that it can freely spin inside its container to coordinate with the earth’s magnetic field, which is why it points north. Because it draws compass needles with north magnetic poles, what people mistakenly refer to as the north magnetic pole is essentially a south magnetic pole.

The field vector’s inclination (I), also known as dip, is the degree to which it is slanted concerning the horizontal. The true east (Y) component, the true north (X) component, the vertical component (Z), and the overall magnetic field strength (F) are the four components of the geomagnetic field.

Nanotesla units (nT) are used to measure the magnetic fields of elements or components F, X, Z, Y, and H. Angles are used to measure inclination (I) and declination (D).

The magnetic fields’ additional components can all be determined from X, Y, and Z. For instance; students can calculate F from the equation, 


Magnetic fields represent the unending magnetic flux lines that travel from northward-pointing magnetic poles to southward-pointing magnetic poles. The lines’ density reveals how strong the magnetic field is. The field lines are congested or more packed at the poles; for instance, the magnetic field is high at the north and south poles of a magnet.

Where the magnetic field is weaker, they spread out and lose density. Parallel straight lines that are evenly spaced apart represent a homogeneous magnetic fields. For students to advance their knowledge in this area, they must have a basic mastery of this topic.

Frequently Asked Questions 

1. What are magnetic field lines?

Ans. Magnetic field lines are the lines that make up a magnetic field; their tangents at different points indicate the direction and amplitude of the field, respectively. They serve as a marker for the magnetic field’s direction. The total amount of magnetic field lines affects how strong the magnetic field is.

2. What is a magnetic field?

Ans. A magnetic field, also known as an electrical charge or electric field, is a vector field that surrounds a magnet and is where magnetic forces are detected. Magnetometer needles and other permanent magnets align in the direction of magnetic fields like the one found on earth. These fields force electrically charged particles to move in a spiral or circular pattern. The functioning of electric motors is caused by this force, which is applied to electrical pulses in wires in magnetic fields.

3. What is magnetic susceptibility?

Ans. A material’s magnetic susceptibility is measured quantitatively by its ability to become magnetised in response to applied magnetic fields. A material’s magnetic susceptibility, typically denoted by the symbol χm, is equal to the ratio of the magnetism M present within the material to the strength of the applied magnetic field H, or χm = M/H. The magnetisation ratio fundamentally includes a particular amount of magnetism per unit volume.

magnetic fields


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