"Day after day, I wondered what electricity was, but didn't find the answer. Eighty years later, I still ask myself the same question, but I can't answer it. (Nikola Tesla)
Electric current does not transfer energy through the flow of electrons in a wire. This is a common misconception. In a copper wire of 1.5 mm2 cross section, free electrons move at a speed of only 0.05 mm/s, and more than 100,000 atoms fit into this segment. If energy is transferred by simple physical collisions of electrons, it takes some time for them to move along the momentum chain. Therefore, the electrons in the wire are just swinging back and forth in almost the same place and are not moving anywhere else. The essence of an electric current is the directed (ordered) movement of charge carriers. The subsequent electromagnetic interaction between charged particles does not take place directly, but through electromagnetic fields. As a result, the current travels at a much higher speed than the motion of the charge carriers, almost reaching the speed of light.
From this it is clear that the current is not the movement of electrons along the wire. The wire is only the carrier of the current. In a circuit, the charge carriers do not need to move inside the wire. Instead, energy is transmitted in the circuit in the form of electromagnetic waves. Such electromagnetic waves can travel in a vacuum or through electrons and other charged particles in a conductor. This process can be described by Maxwell's equations.
In the middle of the 19th century, the English physicist James Clerk Maxwell analyzed all the formulas known at the time to describe electrical and magnetic phenomena. One of them contradicted the others. To reconcile this equation with the others, Maxwell proposed a new theory that electricity and magnetism were unified phenomena and could be described by a set of equations. This theory became electromagnetism, describing the interaction of electricity and magnetism and predicting the existence of electromagnetic waves. These electromagnetic waves are generated by changing electric and magnetic fields and can travel through space and produce an electric current when they reach a receiver.
In an electric circuit, changing electric and magnetic fields are generated by a power supply or other sources. These fields propagate along the wire and produce a current when they reach the load. Therefore, the speed of current transmission is not determined by the speed of the charge carriers, but by the speed of propagation of the electromagnetic field. This speed reaches almost the speed of light and is much faster than the movement of the charge carriers.
To make all the formulas consistent, Maxwell introduced a new physical quantity called electromagnetic waves. He predicted that electromagnetic waves would travel at the speed of light and alternate between electric and magnetic fields.
This prediction proved to be correct because in subsequent experiments, radio waves and other forms of electromagnetic waves were discovered that propagate through air, water and vacuum and can be converted into useful information in the receiver.
But, most importantly, electromagnetic waves do not require wires to transmit power. In fact, the wire is only the carrier of the electricity, which transmits the energy in the electromagnetic waves.
This explains why, on high-voltage transmission lines, electricity can be transmitted over distances of hundreds of kilometers, even though the electrons do not move. Power companies use transformers to convert the energy in high-voltage transmission lines into lower voltages suitable for domestic and industrial use.
The nature of electromagnetic waves
Electromagnetic waves have many different properties, including frequency, wavelength, amplitude and phase. They are defined by fluctuation periods, peaks and valleys, and these quantities reflect changes in the electric and magnetic fields.
Frequency is the number of wave crests passing per second, in Hertz (Hz). Wavelength is the distance required for one complete wavelength. Amplitude is the maximum amplitude of the wave, while phase is the offset of the waveform with respect to a reference point.
Different frequencies and wavelengths will produce different electromagnetic radiation, and the energy and impact factors of these radiations are also different. For example, radio waves, microwaves and infrared rays are all electromagnetic waves, but they have different frequencies and wavelengths, so they have different properties and uses.
Application of electromagnetic waves
Electromagnetic waves have many important applications. Radio communications, radio and television broadcasting all rely on electromagnetic waves. Satellite communications, radar and navigation systems also use electromagnetic waves.
In addition, many diagnostic and therapeutic methods in the medical field also utilize electromagnetic waves. x-rays, MRI and CT scans are all methods that use different forms of electromagnetic waves to capture images and diagnose diseases.
Therefore, the current is not a flow of electrons, but a flow of charges. The charge can be electrons, ions or other charged particles. Electric current does not flow directly through a wire. Instead, energy is transferred through an electromagnetic field, and this transfer is much faster than the movement of electrons through the wire. This type of electrical conduction is the basis of how we use electrical appliances and is an important concept for electrical engineers to understand in depth.
Although we still have many unanswered questions about the nature of electricity, our understanding of electricity is sufficiently advanced to allow us to develop powerful electronic devices and electrical systems. The field of electricity will continue to be a field of challenge and opportunity for future scientists and engineers.