Is Magnetic Field Constant: 7 Interesting Facts

There exists magnetic field all around us. Here, our main aim is to discuss some interesting facts on ‘Is Magnetic Field Constant?’

The strength of the magnetic field at any region is the core factor determining whether the magnetic field is constant or not. If it remains the same throughout, the constant magnetic field is said to exist. A constant magnetic field is obtained if the force due to which the magnetic field is produced is constant.

Different situations when magnetic field remains constant with certain examples will be discussed below.

Does the magnetic field stay constant?

It is not necessary that magnetic field remain constant throughout. Although Earth’s magnetic field is considered to be uniform over a wide region, it is always fluctuating and changes with respect to different locations as well as time.

Magnetic field can be made to stay constant by generating them using a long cylindrical coil of wire. Hence constant currents can produce constant magnetic fields.

When is magnetic field constant?

Magnetic field is constant in situations where the current source that produces magnetic field is constant. A current carrying wire produces magnetic field. Similarly, a long coil of wire through which flows the current generates a constant magnetic field all along inside.

Why is magnetic field constant?

Magnetic field is constant because static fields are generated from constant current sources. By Ampere’s circuital law, the current flowing through a wire is capable of generating a static magnetic field around the wire.

Why magnetic field is not constant?

There are cases where magnetic field does not remain constant. Consider our Earth’s magnetic field. It is practically considered to be constant over a wide area. But in reality, it is not constant but fluctuating with time as well as at different locations.

Earth’s magnetic field is developed due to the current flowing through the inner molten iron and nickel core. But whenever the fluid motion changes or there are any fluctuations, the resultant magnetic field will also be different.

Recent studies are more into studying the fluctuations of Earth’s magnetic field. Such studies can reveal about the nature of inner core of our Earth and its properties.

How to create a constant magnetic field?

 Constant magnetic fields are created when the force behind the generation of magnetic field is constant. A constant magnetic field is easily obtained using a long cylindrical coil of wire. When current is made to pass through the coil or wire, magnetic field is produced and throughout the central hollow region of the coil, magnetic field is constant.

The long cylindrical coil of wire is sometimes referred to as the solenoid, and its behavior (magnetic moment) is similar to a bar magnet.

Examples of constant magnetic field

Here are few examples of constant magnetic field:

  • Magnetic field produced within the inner hollow region of a current carrying long cylindrical coil of copper wire

A current carrying long cylindrical coil is often termed as a solenoid. It produces uniform magnetic field inside the coil and its behavior can be related to a bar magnet. Nevertheless, at its ends and outside the coil, magnetic field may not remain constant.

  • Magnetic field produced due to a constant current source

Ampere’s circuital law tells us that constant current can generate static magnetic fields. Hence, constant magnetic field lines can be obtained using a constant current source.

  • Earth’s magnetic field

Earth’s magnetic field over a wide area is considered to be constant. But, actually the magnetic field due to Earth’s core is varying continuously and the value of magnetic field at different locations is different.

is magnetic field constant
Earth’s Magnetic Field
Image Credits: Wikimedia Commons

Does Earth’s magnetic field constant or vary?

Earth’s magnetic field is not constant and changes with time as well as location. The Earth’s magnetic field is due to the presence of molten iron core. Electricity currents that flow through core is the reason behind the presence of magnetic field.

The magnetic field of the Earth passes through the core and also through the crust and space outward, but in the regions of crust and space, the strength of magnetic field gets weaker compared to the strength at the core.

The Earth’s magnetic field is different at different places of the Earth due to which it must be measured at almost all places to have an estimate of the distribution of magnetic field at different locations.

Is magnetic field constant in a solenoid?

Inside the hollow region of the solenoid, the magnetic field lines are represented by parallel lines. The equally spaced parallel lines signify that the magnetic field is uniform or constant inside the solenoid.

A solenoid is basically a long coil containing many circular loops made of insulated copper wire. As the current passes through the wire, the magnetic field lines are produced according to the Ampere-circuital law and these field lines resemble the magnetic field produced by a bar magnet.

Constant Magnetic Field Inside A Solenoid
Image Credits: Wikimedia Commons

It is to be noted that outside the solenoid the magnetic field is very weak and feeble in comparison to the magnetic field produced inside. Hence for practical purposes, the field outside a solenoid is considered as zero.


To bring to a conclusion, we have briefly discussed certain facts on “Is Magnetic Field Constant?”. This article highlights different cases where magnetic field is constant and where it is not. A brief idea on Earth’s magnetic field and the magnetic field due to solenoid is given.

Deeksha Dinesh

Hello, I am Deeksha Dinesh, currently pursuing post-graduation in Physics with a specialization in the field of Astrophysics. I like to deliver concepts in a simpler way for the readers.

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