How to increase the strength of magnetic field: Different methods and facts


In this post, we’ll mainly focus on how to increase strength of a magnetic field.

The magnetic field intensity depends upon different factors according to the source of the magnetic field. If the source is the solenoid, then the strength of the magnetic field depends upon three factors 1) number of turns per unit length, 2) current 3) the magnetic material inside the core.

If the source is a permanent magnet, it depends upon 1) the dipole moment, 2) the distance from the source 3) the material which surrounds it.

Let’s understand the “solenoid” first. What it is? And how its magnetic field intensity can be determined?

A solenoid is one of the common magnetic devices which is familiar to us.

The name solenoid comes from the Greek word “Solen”, which represents a pipe or channel. It’s an artificial magnet that works on the principle of electromagnetism; when a current passes through a conductor, it creates a circular magnetic field around it. 

How to increase the magnetic field strength of Solenoid

When wires wrapped into coil form, it creates uniform strong magnetic fields similar to the bar magnet around it. The ideal solenoid’s length is very large compared to its diameter to avoid the edge effect.

The solenoid has a uniform magnetic field inside and a negligible magnetic field outside of it.

how to increase strength of a magnetic field
“how to increase strength of a magnetic field”“File:Electromagnetic induction – solenoid to loop – animation.gif” by Ponor is licensed under CC BY-SA 4.0

The magnetic field strength of the solenoid is given by this formula

B=μ0nI

Where, μ0 is the permeability of free space,

n is the number of turns per unit length,

I is the amount of current passing through it.

From the above equation, it can be easily concluded that the strength of the magnetic field of the solenoid mainly depends upon

Three ways to increase the strength of the magnetic field

Current

B∝I

As we can see, the current is solely responsible for producing the magnetic field inside the solenoid. By increasing the amount of the current in the coil, we can strengthen the magnetic field intensity.

Number of turns

B∝n

Each turn (windings) of the solenoid is considered as a circular loop that carries current, and it will be generating a magnetic field around it. The resultant magnetic field of the solenoid is the vector addition of the magnetic field produced by all the windings (turns). It can be concluded that the more the number of turns per unit length, the more magnetic field intensity inside the solenoid.

The material inside the solenoid

Materials respond differently when kept in an external magnetic field, which happens due to the orientation of the dipole moment, which is solely responsible for the change in the magnetic field inside the material. The property of the material which characterizes its response to external magnetic force is known as magnetic permeability.

Magnetic permeability is a property of matter that shows a material’s ability to permit the magnetic field lines to pass through it.

Ferromagnetic material (i.e., iron) has high magnetic permeability, strengthening the magnetic field. Hence, when such material is kept inside the solenoid, which itself is magnetic, it will contribute to the flux of the solenoid, which ultimately results in a strong magnetic field inside the solenoid. 

As we know, the magnetic field intensity (B) inside the solenoid is given by,

B=μ0nI

B∝μ0

Here, μ0  is the magnetic permeability of the air.

We come across some permanent magnets that lose their magnetic field or become weaker as time passes in our daily lives. There are two ways through which we can re-invigorate the weak magnet to the stronger one.

Permanent magnets:

These are the most common source of the magnetic field.

As we know, the atoms in materials consist of electrons and a nucleus, and these electrons revolve around the nucleus forming a tiny current loop that produces a magnetic field. Electrons orbital motion and electrons, atoms, and nuclear spins are also responsible for the cause of magnetic field in these magnetic materials.

Two ways to increase the magnetic field intensity of permanent magnets:

By recharging the magnet

Sometimes, these magnets lose some of their charges, or the domains are not correctly aligned. In this situation, we can increase the strength of the magnetic materials by constantly rubbing with the strong magnet. By doing this, we can easily transfer charges. And also it’ll help to realign the magnetic domains of the weaker magnet which will ultimately increase the strength of the magnetic field.

By stacking together

We can enhance the strength of magnetic field intensity by stacking two or more than two magnets together. In this way, the stacked magnet will have greater intensity.

Let’s see a few examples related to the solenoid.

Problem1: A solenoid has 350 number of turns in 50 cm and consists of four layers. The lower layer has a radius of 1.4 cm. if the current is 6.0 A, Determine the magnitude of magnetic flux density a) inside the solenoid 2) outside the solenoid.

Solution:-  

Given quantities:

L = 50 cm = 0.5 m

r = 1.4 cm = 1.4*10-2 m

I = 6 A

No. of turns per unit length  n=N/L=1000/0.2=5000 turns per meter

The magnitude of B inside the solenoid is given by,

Outside the solenoid, the magnetic field is negligible or zero.

Problem 2: Determine the strength of the magnetic field produced by the solenoid of length 80 cm and a number of turns 360. If the number of turns of the solenoid is increased to 400, then calculate the magnetic field inside the coil.

Solution:-

Given quantities,

N = 360

L = 80 cm = 0.8m

n = N/L= 360/0.8 = 450 turns per meter

I = 15 A

B=?

The magnitude of inside the solenoid is given by;

If the number of turns in solenoid is increased to 400,

n = N/L = 400/0.8 = 500 turns per meter;

From this example, it is evidently seen that as we increase the number of turns, the magnetic field linked inside the solenoid increases.

Problem 3: In the above problem, the current is increased to 20A. Find out the magnetic field inside the solenoid.

Solution:-

Given quantities,

N = 360

L = 80 cm = 0.8m

n = N/L = 360/0.8 = 450 turns per meter

I = 20 A

B=?

The magnitude of inside the solenoid is given by;

Problem 4: A solenoid has a core of magnetic permeability material 6.3 *10-3 H/m. The number of turns in the solenoid is 1000 per meter. A current of 2A flows through the solenoid. Find magnetic intensity in the core.

Solution:-

Given quantities,

μ=6.3*10-3H/m

n = 1000 turns per metre

I = 2 A

B=?

The magnitude of inside the solenoid is given by;

The magnetic field drastically increases when the iron core is kept inside the solenoid.

Frequently asked questions: FAQs

What affects the magnetic field of the solenoid?

The magnetic field intensity of solenoid is greatly affected by three factors; the current passing through it, the density of turns, and the material used as a core.

What is special about the magnetic field of the Solenoid?

The shape of the magnetic field of a solenoid resembles a bar magnet when an electric current passes through it. It has a strong magnetic field inside and an almost negligible magnetic field outside of it.

What is the difference between the solenoid and electromagnet?

The difference between solenoid and electromagnet are,

An electromagnet is a solenoid, but a solenoid need not be an electromagnet. A solenoid is a cylindrical coil; consisting of current-carrying wires (in form of windings or loops) which produce a magnetic field around it. An ideal solenoid has a larger length dimension compared to its diameter.

An electromagnet has a magnetic core, while a solenoid may not have one. A solenoid is considered a type of electromagnet.

What is the difference between a permanent magnet and a solenoid?

Both produce a magnetic field around them but both of them are different in some realm.

A solenoid falls in the category of the temporary magnet as it only generates a magnetic field when the current passes through it, and the magnetic field generated by it is more robust. The great advantage is that we can change its magnetic field as per our needs.As per the name, the permanent magnets have a permanent magnetic field, unlike solenoids; we cannot switch on or off the magnetic field. We cannot change the magnetic field intensity of it. 

What are the uses of the solenoid?

Solenoids that have a soft iron core are suitable electromagnets. It has wide applications, i.e., computer printers, fuel injection, and door locks.

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