Magnetic moment

The magnetic moment of a magnet is a quantity that determines the torque it will experience in an external magnetic field. A loop of electric current, a bar magnet, an electron (revolving around a nucleus), a molecule, and a planet all have magnetic moments.

The magnetic moment may be considered to be a vector having a magnitude and direction. The direction of the magnetic moment points from the south to north pole of the magnet. The magnetic field produced by the magnet is proportional to its magnetic moment. More precisely, the term magnetic moment normally refers to a system's magnetic dipole moment, which produces the first term in the multipole expansion of a general magnetic field. The dipole component of an object's magnetic field is symmetric about the direction of its magnetic dipole moment, and decreases as the inverse cube of the distance from the object.

Definition

The magnetic moment is defined as a vector relating the aligning torque on the object from an externally applied magnetic field to the field vector itself. The relationship is given by

Magnetic dipole

A magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the dimensions of the source are reduced to zero while keeping the magnetic moment constant. It is a magnetic analogue of the electric dipole, but the analogy is not complete. In particular, a magnetic monopole, the magnetic analogue of an electric charge, has never been observed. Moreover, one form of magnetic dipole moment is associated with a fundamental quantum property—the spin of elementary particles.

The magnetic field around any magnetic source looks increasingly like the field of a magnetic dipole as the distance from the source increases.

External magnetic field produced by a magnetic dipole moment

In classical physics, the magnetic field of a dipole is calculated as the limit of either a current loop or a pair of charges as the source shrinks to a point while keeping the magnetic moment m constant. For the current loop, this limit is most easily derived for the vector potential. Outside of the source region, this potential is (in SI units)

Dipole moment

Dipole moment may refer to:

Ronald Jenkees

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Ronald Jenkees is an American composer and musician, best known for his YouTube keyboard performances. His YouTube videos have been viewed (in total) over 70 million times. Jenkees has thus far released four independent albums: the eponymous album Ronald Jenkees (2007), Disorganized Fun (2009), Days Away (2012) and Alpha Numeric (2014).

Musical career

Jenkees began releasing beats and raps online under the name "Big Cheez" in about 2003. Under this name, he produced the 2005 album Straight Laced by Fish. In 2006, Jenkees started posting funny videos on YouTube, and later began posting music-related videos. These videos usually feature him wearing a hat and greeting his viewers by saying, "Hello Youtubes!". His videos gradually gained popularity, particularly after Bill Simmons from ESPN.com featured Jenkees and asked him to record his podcast theme, and again after being "thumbed up" by members of the StumbleUpon community. In 2007, Jenkees independently released his first studio album, Ronald Jenkees. In June 2009, Jenkees was featured on the STS9 album, Peaceblaster: The New Orleans Make It Right Remixes, producing a remix of "Beyond Right Now". On July 31, 2009, Jenkees released his second album, Disorganized Fun. Both are currently available on physical compact discs or as direct MP3 downloads. He has also recorded a third album, Days Away, which was released in 2012, and a fourth, Alpha Numeric, in (2014).

Indian Institute of Technology Joint Entrance Examination

The Indian Institutes of Technology Joint Entrance Examination (IIT-JEE) was an annual engineering college entrance examination in India. It was used as the sole admission test by the 16 Indian Institutes of Technology (IITs) and Indian School of Mines Dhanbad (to be converted into IIT). The examination was organised each year by one of the various IITs, on a round robin rotation pattern. It had a very low admission rate (about 10,000 in 500,000 in 2011), and was thus recognised as one of the toughest examinations in the world.

In 2013 it was replaced by the two-phase Joint Entrance Examination.

History

The first IIT, IIT Kharagpur, started in 1951. In the initial few years (1951-1954) students were admitted on the basis of their academic results followed by an Interview in several Centers across the country. From 1955-1959 admission was via an all India examination held only for IIT Kharagpur (other IITs had not started by then). Branches were allotted through Interviews/counselling held at Kharagpur.