Magnetic field is a special phenomenon that plays a significant role in many applications. Whether in most basic or advanced applications, a proper understanding of this phenomenon is paramount.
A reason this guide explores everything you need to know about magnetic field.
What Are Magnetic Fields
For beginners, we define it as a magnetic object surrounding where a magnetic force is exerted. In simpler terms, these are areas that are invisible around the magnet with the ability to pull or repel other magnetic objects.
We can analyze magnetic fields in two different ways:
As we know from basic mathematical geometry, any vector must possess both magnitude and direction. Magnetic field satisfy this and therefore we can represent it in a drawing by using a grid with several vector sets.
Every single vector point must be unidirectional to the compass. The intensity of the magnetic force will determine how long each vector will be.
Magnetic Field Lines
In as much as they are imaginary, they are located around a magnet. The line density of the field determines the intensity it can possess. The Magnetic field is usually very strong at its poles and weakens as you go further away from the poles.
Origin of Magnetic Fields
Magnetic fields are generated by the motion of certain electric charges, specifically electrons. They are known to contain a negative charge and their motion in a particular way can generate Magnetic fields.
We can find these Magnetic fields situated in the internal structures of magnetic materials. You can also find such fields contained inside wires, a phenomenon we call electromagnetism.
The magnets used in producing Magnetic Fields are usually dipolar, meaning that they contain both North and South poles.
Properties of Magnetic Fields
Magnetic fields have certain properties and characteristics that are unique to them. Let us have a general overview of some of them:
- At no point do any magnetic field lines overlap or intersect with one another
- All the Magnetic Field lines have equal lengths
- Since the Magnetic Fields have magnitude and direction, they qualify to be termed as vector quantities.
- The Magnetic Field lines will follow a path with the least resistance between the North and South Pole.
- Magnetic Fields observe a closed loop kind of path between any two poles.
- There is a significant decrease in the density of the Magnetic Field lines as they move from a higher to lower permeability area.
- Direction of flow of the Magnetic Field is usually from South to North pole in a material. The direction of flow in air is the opposite since it moves from North to the South pole.
- The Magnetic Field in the regions that surround either pole of a magnet is normally very high. This is due to their high concentrations at those points and sparsely dense at the center of the magnetic object.
Measuring Magnetic Fields
There are various that we can use to measure the magnet fields. These include:
Also called a Gaussmeter, we can use it to measure the magnetic field of a specific region. It also has the ability to detect the direction in which the magnetic field lines move.
They can measure various principles depending on the type of Gaussmeter used. A good example is one that measures using the Hall Effect by gauging the strength of a magnetic field using current.
Other Magnetometers make use of the magneto induction effect. This enables them to quantify the rate of magnetization of a material after being subjected to a Magnetic Field.
Finally, we have some that rely on the Magnetoresistance effect. They can determine how a material reacts by changing its electrical after being subjected to a magnetic field.
The difference between this tool and a Magnetometer is that it measures the flux density. As we know, magnetic flux is actually the sum of all the magnetic field going through a specific zone.
It observes Faradays Law of electromagnetic induction. It has a moving coil that operates between two fixed coils which induce a voltage due to its motion.
This change in voltage is captured by a calibration meter. This will quantify the presence of flux that is available in that Magnetic Field.
Unit Of Magnetic Field
The International System Of Measurement (also called the SI unit) for magnets is called the Tesla. This unit can be described as the magnets flux density or the strength possessed by the magnetic field.
We also have various other units that you can use in instances relating to electromagnetism. Such SI Units include the Gauss, 109 gamma or the Maxwell.
Magnetic Field Strength
This is basically the magnetomotive force proportion that can generate flux density in a unit material of a magnet. We can also refer to it as Magnetic Field Intensity.
To know how strong the flux density produced is, we rely on something called the Magnetic Field Strength. The SI Unit for this physical quantity is in amperes per meter (A/m).
We should be careful not to confuse the Magnetic Field Strength with Magnetic Flux Density. However, both terms can be used to express Magnetic Field Intensity.
The main difference between the two is that Magnetic Flux Density (B) is measured in Newton-metres per Ampere (Nm/A). On the other hand, the Magnet Field Strength (H) is expressed in terms of Amperes per metre (A/m).
Effects Of Bringing Two Magnetic Fields Together
When you bring two separate magnets together but not touching, the effect will be a disturbance of both their Magnetic Field lines. This scenario is similar to what happens when you bring different electric charges close, the electric filed lines will be perturbed.
When you bring two similar poles (either N and N or S and S) together, then they are bound to repel each other. This in turn will bend the away from the respective poles.
Bringing opposite poles together will result in the Magnetic Field lines joining thus increasing their density at the poles.
Biological Effects of Magnetic Fields
We can classify the biological effects of Magnetic Fields into two. They can either be physical effects or biological effects.
The physical effects mainly occur when magnetic objects implanted in our bodies or around us are attracted to a Magnetic Field. Implanted objects may include pacemakers, organ implants or even surgical clips screwed in bones.
When exposed to an MRI machine with such in your body, they will be very hazardous in the machines Magnetic Field. When the machine moves at a high speed, the objects tend to align with its Magnetic Field.
This will create a form of torque on the implanted object that may cause grave internal injuries. The ferromagnetism of such objects is usually amplified by their quantity in the body.
Although there is still a dispute as to whether static fields can cause cancer, it is still a subject for further research. But frequent MRI usage has availed data that shows mild reversible impacts of static fields on electrocardiograms.
This is normally brought about by the movement of blood that acts as a conductive medium interacting with the Magnetic Field around the heart. However, the damage caused is negligible and can not be taken as a major concern.
Earth’s Magnetic Field
If you have keenly observed the direction that a compass pinpoints, you will realize that it is always in the Northward direction. All compasses are manufactured with a magnet inside them and their motion is usually facilitated by a magnetic field.
This is a clear sign that all our surrounding has some form of magnetic field. This Magnetic Field is generated by the earth.
Let’s discuss some of the ways that this Magnetic Field from the Earth comes about:
i. The core of the earth has temperature levels that are extremely high. This means that any mineral such as iron found inside there is in a molten state that is infinitely being heated.
The continuous heating of such minerals results in the generation of convection within the heated minerals. This creates convectional currents that convey the charged particles forming a Magnetic Field.
ii. Most of the matter that surrounds the earth’s surface is mostly composed of charged particles. As the earth rotates on its axis, these surrounding particles equally rotate with it.
The motion of these charged particles is normally in continuous current loops. This is what brings about the generation of a Magnetic Field.
iii. The composition of the earth’s atmosphere is several gasses that have been ionized. These gases rotate with the earth.
Any motion of an ionized substance will definitely generate an electric current. The effect is a Magnetic Field generated.
Magnetic Fields Vs Magnetic Force
In as much as they make look similar, Magnetic Fields and Magnetic Force are totally different measures. We can have a comparison of the two by using the example of a charged particle that is contained in a magnetic field.
If we look at the magnetic force it contains when placed in a magnetic field, this is actually any force that is exerted on it. As for the Magnetic Field, we can define it as the area around which the Magnetic Force is exerted on the particle.
When it comes to measuring the two, the SI Unit for measuring the Magnetic Force is usually in Newtons. We measure the strength of the Magnetic Field using Tesla as the SI Unit.
The existence of a Magnetic Force is dependent on the availability of a charged particle that impresses on the force. As for the Magnetic Field, it is always present whether the said charged particle is there or not.
Applications Of Magnetic Fields
This is a machine that produces electric energy by converting it from mechanical energy. The principle in this application is the electromagnetic induction, Michael Faradays invention.
As an electric conductor rotates within a magnetic field, a differential voltage is generated between its ends. An electric current is created when electric charges become mobile due to this voltage difference.
Magnetic Resonance Imaging
An MRI machine is commonly used in hospitals to produce images of internal parts and organs of the human body. The images are generated using both electromagnets and magnetic field.
They can generate images such as of the brain, the heart and many other parts. They are then analyzed to ascertain whether they are normal or defective.
This will include both electric AC and DC motors. The working principle of a DC motor is such that magnetic forces are exerted on any current carrying loop that is positioned within a magnetic field.
A static magnet provides the Magnetic Field with the force exerted triggering a kind of rotation. As for the AC motor, an alternating current is passed through a stator that generates a rotating magnetic field.
The difference between the rotational speed of the stator and the rotor produces an emf on the motor’s rotor. The rotor will continuously rotate so long as it does not match the rotating speed coming from the stator.
Commonly known as Maglev, they are train systems that are known to have the highest speeds in the world. By utilizing the attraction and repulsion mechanisms of magnetism, they levitate above the train tracks.
There is no physical contact with the train therefore friction is eliminated by the magnetic repulsion. The levitation and the trains propulsion using a linear induction motor are made possible by the Magnetic Field.
This is a special type of magnet where an electric current is tasked with the producing a magnetic field. They are able to generate very heavy magnetic fields which is facilitated the several wire turns in their structure.
Their major advantage is that you can easily switch them on and off making them the best choice when lifting very heavy metals. Their applications are very many and vary with different industries like the metal recycling.
As you can see, the knowledge about magnetic field is very critical in the design of various equipment and machines. Of course, the magnetic field strength varies depending on the type of magnet.
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