Question

Q. 3 what kind of a magnetic field produced due to a current carrying straight conductor ?

Answer 1

Hi,
The magnetic field due to current carrying conductor is in the form of closed loops centred at the axis of the conductor. The direction is given by right-hand thumb rule and the magnitude is given by the following relationship:
$B=\frac{{\mu }_{o}I}{2\pi r}$
where r is the distance from the wire.

And as Umakant rightly said, the magnetic field due to any current carrying conductor is temporary. It exists only as long as the current flows through the conductor.