Electromagnetism

While permanent magnets produce a good and sometimes very strong static magnetic field, in some applications the power of this magnetic field is still very weak. We need to be able to control the amount of magnetic flux available. So we need to use electricity to produce a much stronger and more controllable magnetic field.

Using wire coils wrapped or wrapped around a soft magnetic material such as an iron core, we can produce very powerful electromagnets for use in many different electrical applications. This use of wire coils produces us a relationship between electricity and magnetism, another form of magnetism called electromagnetism.

Electromagnetism is produced when it flows through a simple conductor, such as an electric current, a wire or cable length, and a magnetic field is created throughout the entire conductor as the current passes through the entire conductor. The small magnetic field created around the conductor has a certain direction with both the "North" and "South" poles determined by the direction of the electric current flowing through the conductor. Therefore, it is necessary to establish a relationship between the current flowing from the conductor and the magnetic field produced by this current flow formed around it, allowing us to define the relationship between Electricity and Magnetism as Electromagnetism.

When an electric current passes through a conductor, we determined that a circular electromagnetic field is produced around it with magnetic flux lines that form full loops that do not pass along the entire length of the conductor.

The rotational direction of this magnetic field is governed by the direction of the current flowing from the conductor, and the corresponding magnetic field produced is stronger near the center of the current-carrying conductor. This is due to the fact that the path length of the loops is larger as it moves away from the conductor, resulting in weaker flux lines, as shown below.

Magnetic Field Around a Conductor

Electromagnetism
Magnetic Field Around a Conductor

A simple way to determine the direction of the magnetic field around the conductor is to consider screwing an ordinary wooden screw into a paper. When the screw enters the paper, the rotational movement occurs CLOCKWISE, and the only part of the screw that appears on the paper is the head of the screw.

If the wooden screw has a pozidriv or philips type head design, the cross on the head will be visible. This cross is used to indicate that the current flows "inside" the paper and away from the observer.

Electromagnetism

Likewise, the action of removing the screw is counterclockwise. Since the current enters from the top, it comes out from under the paper, and the only part of the wooden screw visible from below is the tip or point of the screw. This point is used to indicate that the current flows "out".

Next, the physical action of screwing the tree screw in and out of the paper indicates the direction of the current in the conductor and therefore the direction of rotation of the electromagnetic field around it, as shown below. This concept is commonly known as Right Hand Screw.

Right Hand Screw

Electromagnetism

The magnetic field implies the existence of two poles, north and south. The polarity of a current-bearing conductor can be determined by drawing the uppercase letters S and N, and then by adding arrowheads to the free end of the letters, as shown above, which gives a visual representation of the magnetic field direction. Another more familiar concept that determines both the direction of the current flow and the direction of the magnetic flow around the conductor is called the "Left Hand Rule".

Electromagnetism
Left Hand Rule

The recognized direction of a magnetic field is from the north pole to the south pole. This direction can be removed by holding the current-bearing conductor in your left hand, holding the direction of the thumb elongated electron flow from negative to positive.

The position of the fingers extending along and around the conductor will show the direction of the magnetic force lines created, as shown now.

If the direction of the electron passing through the conductor is inverted, the thumb of the left hand will need to be placed on the other side of the conductor to indicate the new direction of the electron current flow. In addition, as the current is reversed, the direction of the magnetic field around the conductor will be inverse because, as we have said before, the direction of the magnetic field depends on the direction of flow of the current.

This "Left Hand Rule" can also be used to determine the magnetic direction of the poles in an electromagnetic coil. This time, the fingers show the direction of the electron flow from negative to positive, while the elongated thumb indicates the direction of the north pole. This rule has a variation called the "right hand rule", which is based on the traditional current flow (positive to negative).

Consider that a single piece of flat wire bends into a single loop, as shown below. Although the electric current flows in the same direction along the entire length of the conductor, it will flow in opposite directions from the paper. This is because the current leaves the paper on one side and enters the paper on the other. Therefore, a clockwise area and counterclockwise area are produced along the paper sheet side by side.

The gap between these two conductors becomes an "intensified" magnetic field, where the lines of force are propased to form a rod magnet that forms a pronounced north and south pole at the intersection.

Electromagnetism Around a Loop

Electromagnetism
Electromagnetism Around a Loop

The current flowing through the two parallel conductors of the loop is in opposite directions as the current passing through the loop exits the left side and rotates from the right side. This causes the magnetic field around each conductor in the loop to be "IDENTICAL" to each other.

The resulting force lines generated by the current flowing through the loop contrast in the space between the two conductors, where two similar poles meet, thereby deforming the force lines around each conductor as shown.

However, the deterioration of the magnetic flow between the two conductors causes the density of the magnetic field in the middle connection when the force lines become closer together. The interaction between two similar areas produces a mechanical force between two conductors that try to move away from each other. This propulsion of these two magnetic fields in an electric machine produces movement.

Electromagnetism

However, since conductors cannot move, two magnetic fields help each other by forming a north and a south pole along this line of interaction. This causes the magnetic field to be the strongest in the middle between the two conductors. The density of the magnetic field around the conductor is proportional to the distance from the conductor and the amount of current passing through it.

The magnetic field created around the wire carrying a stream of a flat length is very weak, even if high current passes through it. However, if several nooses of the wire are wrapped together along the same axis, a wire coil is produced, the resulting magnetic field will become even denser and stronger than a single noose. This produces an electromagnetic coil, more commonly called Solenoid.

Then the wire of any length has an electromagnetism effect around itself when an electric current passes through it. The direction of the magnetic field depends on the direction of flow of the current. By turning the length of the wire into a coil, we can increase the strength of the generated magnetic field, and we will look at this effect in more detail in the next article.