Rotating Magnetic Field

Introduction to Rotating Magnetic Field:

A rotating magnetic field is a kind of magnetic field which ideally changes its direction at an angular rate which is constant. In the working of a motor that works on alternating current, the rotating magnetic field plays a key role as it is associated with its principle of operation. The concept of rotating magnetic field was introduced by Nikola Tesla in 1882. Galileo Ferrari's has done his research independently to introduce some more features of this concept in 1885.



Production of Rotating Magnetic Field


A rotating magnetic field which is symmetric can be produced using as few as three coils. To produce a rotating magnetic field, three coils should be driven by a symmetric three phase a.c. current and one of the phases is shifted to 120 degrees as compared to the other phase. In this case the magnetic filed should be taken as the linear function of the current which is flowing in the coil. The three phases which are 120 degrees out of phase compare to each other when applied to the axis of the alternating current motor then it produces a single rotating vector. This rotating vector follows the magnetic field in the coil and hence produces a rotating magnetic field .



Application of Rotating Magnetic Field


Rotating magnetic fields can also be used in the induction motors because the magnets, which are used, degrades with time and the induction motor use the short circuited rotor instead of a magnet, which is easily follow the rotating magnetic field produced by a stator, which is multi coiled. In the case of the induction motor, the turns of the rotor which is short circuited, develops the eddy current in the rotating magnetic field of the stator which is used to move the rotor by the developed Lorentz force. Such motors are generally not synchronous but they have involved a necessary degree of the slip by which the current will be produced due to the relative motion of the field and the rotor.

Magnetic Field Moment

Introduction to magnetic field moment:

Magnetic moment is a determination of its propensity to align through magnetic field. Equally the magnetic moment also magnetic field might be measured towards vectors which contains a magnitude and the direction. The way of the magnetic moment point as of the south within the way of north pole of a magnet. Magnetic field created through a magnet is relative toward its magnetic moment. I like to share this Effective Magnetic Moment with you all through my article.


Magnetic field moment


For instance, circles of electric current, an electron, a tavern magnet, also planet all contain magnetic moments.

Further accurately, the word magnetic moment usually refers toward a system magnetic dipole moment, which it is; create the initial word within the multiple extension of a common magnetic field. Dipole part of object's magnetic field be symmetric on the way of magnetic dipole moment, also reduce like the inverse dice of the distance as of the object.

Magnetic moment of solenoids:

Magnetic moment of a number of turn solenoid is resolute when the vector total of the instant of entity rotates. In the case of the same rotation, it is equivalent just towards the entity that turns instant multiply through the whole number of rotation within the solenoid. Formerly, the value of sum magnetic instant is established, it will be used to create the distant field also to store energy within the outside field and within the similar approach like used for the single-turn circle. Having problem with Centripetal Acceleration Equation keep reading my upcoming posts, i will try to help you.

Type of magnetic sources:

Motion of electric charges.
Intrinsic magnetism of elementary particles.

Magnetic dipole moment


Since the term used for the torque lying on an existing circle, the uniqueness of the existing loop be summarized within its magnetic instant.

`mu=IA`

Magnetic instant be able to be measured toward exist a vector quantity through the way vertical to the current circle within the right-hand-rule way.

Torque is known through,

`tau=muxB`

When we see within the geometry of an existing circle, this torque be inclined to line up the magnetic instant through the magnetic field B, thus this correspond to its lowly energy configuration. Potential energy related through the magnetic moment can be written as,

`U(theta)=-mu.B`

Thus, the distinction within energy among aligned also be anti-aligned,

`DeltaU=2muB`

Magnetic Field of the Earth

Introduction to Magnetic field of earth

Sir William gilbert was the first to suggest in year 1600, that earth itself is a huge magnet. His statement was based on the following evidence:

I. A magnet suspended from a thread and free to rotate in the horizontal plane comes to rest along the north-south direction. On disturbing, the magnet returns quickly to its north-south direction. This is as if a huge magnet lies along the diameter of earth. The north pole of this fictitious magnet must be towards geographical south so as to attract south pole of the suspended magnet and vice-versa.

II.When a soft iron piece is buried under earth’s surface in the north south direction, it is found to acquire the properties of a magnet after some time.I like to share this Magnets Rare Earth with you all through my article.

III.When we draw field lines of a magnet, we come  across neutral points. At these points, magnetic field due to the magnet is neutralized or cancelled exactly by the magnetic field of earth. If earth has no magnetism of its own, we would never observe neutral points.

Cause of Magnetic Field of the Earth

The exact cause of earth magnetism is not yet known. However, some important postulates in this respect are as follows:

a) According to Prof. Brackett, earth’s magnetism may be due to rotation of about its axis. This is because every substance is made up of charged particles. Therefore, a substance rotating about its axis is equivalent to circulating currents, which are responsible for the magnetization.

b)In the outer layers of the earth’s atmosphere, gases are in the ionized state, primarily on account of cosmic rays. As earth rotates, strong electric currents are setup due to movement of ions. These currents might be magnetizing the earth.Is this topic Transverse Waves and Longitudinal Waves hard for you? Watch out for my coming posts.

c)The earth’s core is very hot and molten. Circulating ions in the highly conducting liquid region of the earth’s core could form current loops and produce a magnetic field.

General Features of Earth’s Magnetic Field

It has been established that earth’s magnetic field is fairly uniform. The strength of this magnetic field at the surface of earth is approximately 10-4 tesla or 1 gauss. The field is not confined only to earth’s surface, it extends upto a height nearly 5 times the radius of earth.  At present the south pole of earth is located at a place on north Canada, longitude 960 W and latitude 70.50 N and the north pole is located diametrically opposite the south pole i.e. at longitude 840 E and latitude 70.50 S. The magnetic poles are approximately 2000 km away from geographic poles.