wire when coiled acts as electromagnet but shot circuit takes place when not coiled? y?

dhruba sunuwarthe same wire is not formed a coil and supplied voltage short circuits!

Says who? For DC current it is irrelevant whether it is a coil or straight. The resistance and hence the current will be the same. There is no short circuit.

A.V.RamaniSays who? For DC current it is irrelevant whether it is a coil or straight. The resistance and hence the current will be the same. There is no short circuit.

i had heard someone say this... and the person was very confident... was confused and asked.. theoretically i was sure but i thought there might be some reason... so i posted here.. thank you sir!

yes magnetic field exits in both cases.
this can be explained by right hand thumb rule for "Magnetic Field due to a Current through a Straight Conductor"

here the thumb indicates the direction of current and the rest of fingers indicates the direction of magnetic field.
In Magnetic Field due to a Current through a Circular Loop
This case can be explained by the maxwell's corkscrew rule
We know that the magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it. Therefore, if there is a circular coil having n turns, the field produced is n times as large as that produced by a single turn. This is because the current in each circular turn has the same direction, and the field due to each turn then just adds up.

dhruba sunuwartheoretically i was sure but i thought there might be some reason..

The situation changes with AC depending on the coil geometry (Radius, number of turns and such) and frequency there will be an inductance that comes into picture. Normal Ohm's law will not apply if the Ohmic resistance alone is considered.