A special form of the existence of matter - the Earth's magnetic field contributed to the origin and preservation of life. Fragments of this field, pieces of ore, attracting iron, led electricity to the service of humanity. Without electricity, survival would be unthinkable.
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What are lines of magnetic induction
The magnetic field is determined by the strength at each point in its space. Curves that unite field points with equal in magnitude strengths are called lines of magnetic induction. The magnetic field strength at a particular point is a power characteristic, and the magnetic field vector B is used to evaluate it. Its direction at a particular point on the magnetic induction line occurs tangentially to it.
If a point in space is affected by several magnetic fields, then the intensity is determined by summing the magnetic induction vectors of each acting magnetic field. In this case, the intensity at a particular point is summed up in absolute value, and the magnetic induction vector is defined as the sum of the vectors of all magnetic fields.
Despite the fact that the lines of magnetic induction are invisible, they have certain properties:
- It is generally accepted that the magnetic field lines exit at the pole (N) and return from (S).
- The direction of the magnetic induction vector is tangential to the line.
- Despite the complex shape, the curves do not intersect and necessarily close.
- The magnetic field inside the magnet is uniform and the line density is maximum.
- Only one line of magnetic induction passes through the field point.
The direction of the lines of magnetic induction inside a permanent magnet
Historically, in many places on the Earth, the natural quality of some stones to attract iron products has long been noticed. Over time, in ancient China, arrows carved in a certain way from pieces of iron ore (magnetic iron ore) turned into compasses, showing the direction to the north and south poles of the Earth and allowing you to navigate the terrain.
Studies of this natural phenomenon have determined that a stronger magnetic property lasts longer in iron alloys. Weaker natural magnets are ores containing nickel or cobalt. In the process of studying electricity, scientists learned how to obtain artificially magnetized products from alloys containing iron, nickel or cobalt.To do this, they were introduced into a magnetic field created by direct electric current, and, if necessary, demagnetized by alternating current.
Products magnetized in natural conditions or obtained artificially have two different poles - the places where magnetism is most concentrated. Magnets interact with each other by means of a magnetic field so that like poles repel and unlike poles attract. This generates torques for their orientation in space of stronger fields, for example, the Earth's field.
A visual representation of the interaction of weakly magnetized elements and a strong magnet gives the classic experience with steel filings scattered on cardboard and a flat magnet underneath. Especially if the sawdust is oblong, it is clearly seen how they line up along the magnetic field lines. By changing the position of the magnet under the cardboard, a change in the configuration of their image is observed. The use of compasses in this experiment further enhances the effect of understanding the structure of the magnetic field.
One of the qualities of magnetic lines of force, discovered by M. Faraday, suggests that they are closed and continuous. Lines coming out of the north pole of a permanent magnet enter the south pole. However, inside the magnet they do not open and enter from the south pole to the north. The number of lines inside the product is maximum, the magnetic field is uniform, and the induction may weaken when demagnetized.
Determining the direction of the magnetic induction vector using the gimlet rule
In the early 19th century, scientists discovered that a magnetic field is created around a conductor with current flowing through it. The resulting lines of force behave according to the same rules as with a natural magnet.Moreover, the interaction of the electric field of a conductor with current and the magnetic field served as the basis of electromagnetic dynamics.
Understanding the orientation in space of forces in interacting fields allows us to calculate the axial vectors:
- magnetic induction;
- The magnitude and direction of the induction current;
- Angular speed.
This understanding was formulated in the gimlet rule.
Combining the translational movement of the right-hand gimlet with the direction of the current in the conductor, we obtain the direction of the magnetic field lines, which is indicated by the rotation of the handle.
Not being a law of physics, the gimlet rule in electrical engineering is used to determine not only the direction of the magnetic field lines depending on the current vector in the conductor, but also vice versa, determining the direction of the current in the solenoid wires due to the rotation of the magnetic induction lines.
Understanding this relationship allowed Ampère to substantiate the law of rotating fields, which led to the creation of electric motors of various principles. All retractable equipment using inductors follows the gimlet rule.
Right hand rule
Determining the direction of a current moving in a magnetic field of a conductor (one side of a closed loop of conductors) clearly demonstrates the right hand rule.
It says that the right palm, turned to the N pole (field lines enter the palm), and the thumb deflected 90 degrees shows the direction of movement of the conductor, then in a closed circuit (coil) the magnetic field induces an electric current, the motion vector of which four fingers point.
This rule demonstrates how DC generators originally appeared. A certain force of nature (water, wind) rotated a closed circuit of conductors in a magnetic field, generating electricity. Then the motors, having received an electric current in a constant magnetic field, converted it into a mechanical movement.
The right hand rule is also true for inductors. The movement of the magnetic core inside them leads to the appearance of induction currents.
If the four fingers of the right hand are aligned with the direction of the current in the turns of the coil, then the thumb deviated by 90 degrees will point to the north pole.
The rules of the gimlet and the right hand successfully demonstrate the interaction of electric and magnetic fields. They make it possible to understand the operation of various devices in electrical engineering for almost everyone, not just scientists.
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