if work done by magnetic field is zero, then how does a magnet attract objects? who is responsible for the work done?

Asked by Baishali Baruah | 21st Jun, 2014, 12:41: PM

Expert Answer:

The working of a magnet can be understood when we look in the atomic scale. In the vicinity of the nucleus of an atom, there are electrons revolving. These electrons occupy certain shells that surround the nucleus. These shells have been given letter names K,L,M, etc.

Within the shell, there exists sub-shells or orbitals such as s,p,d,f. Some of these orbitals look like spheres, some like an hourglass, and so on. The K shell has an s orbital - 1s. The L shell has an s and p orbital - 2s and 2p. The M shell has an s, p and d orbital - 3s, 3p and 3d orbital. These orbitals also have various sub-orbitals.

Now, each such orbitals can contain only a certain number of electrons. A maximum of 2 electrons can occupy a sub-orbital where one is a spin up and the other is a spin down. There can not be two electrons with spin up in the same sub-orbital. This is in accordance with the Pauli's exclusion principal.

Also, when you have a pair of electrons in a sub-orbital, their combined magnetic fields cancel each other. The valence orbital in any atom will have one or more than one unpaired electrons which result in the magnetic field as electrons are charges and moving charges produce magnetic field around them. This is the origin of magnetism in materials and larger the unpaired number of electrons, larger is the magnetism.

Answered by Romal Bhansali | 2nd Jul, 2014, 11:33: AM

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