We know that these are two different fundamental forces of nature, so naturally they behave in a different manner.
In the case of electromagnetic force, the strength varies inversely to the distance squared.
In the case of strong force, the strength increases as the distance between the quarks increases (consequences of Asymptotic freedom).
I want to know the explanation for that.
Ananya,
the conclusion you "have (almost) come to" is correct, but let me add something.
Indeed, in the case of QCD the virtual cloud around a given colour charge, say a quark q, contains both quark-antiquark pairs and and gluons, both having colour charges (while in QED photons in the cloud do not have electric charge). The effects of the two components of the QCD cloud on the variation of effective colour charge with the distance are opposite. Virtual quark antiquark pairs make it decrease, like in QED, gluons make it increase. The total effect (increase or decrease) depends on the number of quark flavours nf contributing. Gluons win if (33-2nf)>0. The number of contributing flavours depends on energy, but is at maximum nf=6. Hence gluons win. However, this is not a basic principle. In an hypothetical world with many more quark flavours, say nf=18 for example, the colour force would decrease with increasing distance at energies at which all flavours contribute.
To answer your question in one line:
This is precisely the difference between an (unbroken) abelian gauge theory and an (unbroken) non-abelian theory.
A nice historical account of QCD has been recently presented by John Ellis (arXiv : 1409.4232). Second and third paragraphs of Sec 2 contains the qualitative answer. If you want the details, follow the references there.
1. "In the case of electromagnetic force, the strength varies inversely to the distance squared." - Sorry! It is not always so, the magnetic force changes as R^-3
2. The strong and el. mag. forces actually have the same nature. Its different behaviour are conditioned with different GEOMETRY of fields. The First and second types are peculiar to localized fields in same time (some of elementary particles.) The non localised fields (photons) may have a second type only. You can check here: http://vixra.org/author/george_kirakosyan
Ananya,
the conclusion you "have (almost) come to" is correct, but let me add something.
Indeed, in the case of QCD the virtual cloud around a given colour charge, say a quark q, contains both quark-antiquark pairs and and gluons, both having colour charges (while in QED photons in the cloud do not have electric charge). The effects of the two components of the QCD cloud on the variation of effective colour charge with the distance are opposite. Virtual quark antiquark pairs make it decrease, like in QED, gluons make it increase. The total effect (increase or decrease) depends on the number of quark flavours nf contributing. Gluons win if (33-2nf)>0. The number of contributing flavours depends on energy, but is at maximum nf=6. Hence gluons win. However, this is not a basic principle. In an hypothetical world with many more quark flavours, say nf=18 for example, the colour force would decrease with increasing distance at energies at which all flavours contribute.
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