One of the most important sections of modern physicsare electromagnetic interactions and all related definitions. It is this interaction that explains all electrical phenomena. The theory of electricity covers many other sections, including optics, because light is electromagnetic radiation. In this article we will try to explain the essence of electric current and magnetic force in an accessible, understandable language.
As a child, adults showed us differentfoci with the use of magnets. These amazing figures, which are attracted to each other and can attract small toys to themselves, always pleased the children's eyes. What are magnets and how does the magnetic force act on the iron parts?
Explaining with scientific language, it is necessary to turn toone of the basic laws of physics. According to Coulomb's law and the special theory of relativity, a certain force acts on the charge, which directly depends on the speed of the charge itself (v). It is this interaction that is called the magnetic force.
In general, it should be understood that any magneticphenomena arise only when charges move inside the conductor or when currents are present in them. When studying magnets and the definition of magnetism itself, it should be understood that they are closely related to the phenomenon of electric current. So let's figure out the essence of the electric current.
Electric force is the force thatacts between an electron and a proton. It is numerically much larger than the value of the gravitational force. It is generated by an electric charge, or more precisely, by its motion inside the conductor. Charges, in turn, are of two kinds: positive and negative. As is known, positively charged particles are attracted to a negatively charged one. However, charges of the same sign have the property of repelling.
So, when the guide starts to movethese same charges, it generates an electric current, which is explained as the ratio of the amount of charge flowing through the conductor in 1 second. The force acting on a conductor with a current in a magnetic field is called the Ampère force and is governed by the "left hand" rule.
Magnetic interaction can beeveryday life when dealing with permanent magnets, inductors, relays or electric motors. Each of them has a magnetic field that is invisible to the eyes. It can be traced only by its action, which it exerts on moving particles and on magnetized bodies.
The force acting on a conductor with a current inmagnetic field, was studied and described by the French physicist Ampere. In honor of him, not only this force, but also the magnitude of the current is named. In school, Ampère's laws are defined as the rules of the "left" and "right" hands.
It should be understood that the magnetic field is alwaysarises not only around the sources of electric current, but also around the magnets. It is usually depicted with the help of magnetic lines of force. Graphically, it looks as if a sheet of paper was placed on a magnet, and sawdust was filled on top of the iron. They will take exactly the same form as in the picture below.
In many popular books on physics, forcemagnetic is introduced as a result of experimental observations. It is considered a separate fundamental force of nature. Such a representation is erroneous, in fact the existence of a magnetic force follows from the principle of relativity. Its absence would lead to a violation of this principle.
In magnetic force there is nothing fundamental - it is simply a relativistic consequence of Coulomb's law.
If you believe the legend, in the first century of our era onthe island of Magnesia, the ancient Greeks discovered unusual stones that possessed amazing properties. They attracted to themselves any things made of iron or steel. The Greeks began to take them from the island and study their properties. And when the stones fell into the hands of street magicians, they became indispensable helpers in all their speeches. Using the forces of magnetic stones, they managed to create a whole fantastic show, which attracted a lot of spectators.
As the stones spread throughout theparts of the world, they began to go about legends and myths. Once the stones were in China, where they were named after the island on which they were found. Magnets became the subject of study of all the great scientists of the time. It was noticed that if you put a magnetic ironstone on a wooden float, fix it, and then turn it, then it will try to return to its original position. Simply put, the magnetic force acting on it will turn the ironstone in a certain way.
Using this property of magnets, scientists came up withcompass. On the round form, made of wood or cork, two main poles were drawn and a small magnetic needle was installed. This design was lowered into a small bowl filled with water. Over time, compass models have been refined and become more accurate. They are used not only by seafarers, but also by ordinary tourists who like to explore the desert and mountainous terrain.
Scholar Hans Oersted almost all his lifededicated to electricity and magnets. Once during a lecture at the university, he showed his students the following experience. Through an ordinary copper conductor, he missed the current, after a while the conductor warmed up and began to bend. This was the phenomenon of the thermal property of an electric current. The students continued these experiments, and one of them noticed that the electric current has another interesting property. When the current flowed in the conductor, the arrow of the compass next to it began to gradually deviate. Studying this phenomenon in more detail, the scientist discovered the so-called force acting on the conductor in a magnetic field.
Scientists have made attempts to find a magneticcharge, but the isolated magnetic pole could not be detected. This is explained by the fact that, unlike electric, magnetic charges do not exist. Otherwise, it would be possible to separate a single charge by simply breaking off one of the ends of the magnet. However, at the other end a new opposite pole is formed.
In fact, any magnet representsa solenoid on whose surface the intra-atomic currents are circulating, they are called Ampere currents. It turns out that a magnet can be considered as a metal rod, through which a constant current circulates. It is for this reason that the introduction of an iron core into the solenoid greatly increases the magnetic field.
Like any physical phenomenon, a magnetic fieldhas the energy that it takes to move the charge. There is the concept of EMF (electromotive force), it is defined as the work of moving a unit charge from point A0 to point A1.
The EMF is described by the Faraday laws, which are applied in three different physical situations:
Numerically, the EMF by the Faraday formula is equal to: EMF = W / q.
Consequently, the electromotive force is notforce in the literal sense, since it is measured in Joules on the Coulomb or in the Volts. It turns out that it is an energy that is transmitted to the conduction electron when the circuit is traversed. Each time, making a regular round of the rotating frame of the generator, the electron acquires energy numerically equal to the EMF. This additional energy can not only be transmitted by collisions of atoms of the external chain, but also be released as a Joule heat.
The force acting on the current in a magnetic field,is determined by the following formula: q * | v | * | B | * sin a (the product of the magnetic field charge, the velocity moduli of the same particle, the field induction vector and the sine of the angle between their directions). The force that acts on a moving unit charge in a magnetic field is commonly called the Lorentz force. It is interesting that the third law of Newton is invalid for this force. It obeys only the law of conservation of momentum, which is why all the tasks of finding the Lorentz force should be solved proceeding from it. Let's figure out how to determine the strength of the magnetic field.
To find the force that arises aroundconductor with current, it is necessary to know several quantities: the charge, its speed and the value of the induction of the emerging magnetic field. The next task will help to understand how to calculate the Lorentz force.
Determine the force acting on the proton, which moves at a speed of 10 mm / s in a magnetic field by induction 0.2 Cl (the angle between them is 90aboutsince the charged particle moves perpendicular to the lines of induction). The solution reduces to finding a charge. Looking at the table of applications, we find that the proton has a charge of 1.6 * 10-19 Cl. Further, we calculate the force by the formula: 1.6 * 10-19 * 10 * 0.2 * 1 (the sine of a right angle is equal to 1) = 3.2 * 10-19 Newtonian.
