Question

Why magnetic field is created due a current carrying conductor?

Answer 1

Any current carrying conductor produces a magnetic field circulating around itself according to the grip version of the Right-hand rule (if the conventional current is in the direction of the thumb, the fingers curl in the direction of the magnetic field). If you imagine moving your thumb around around a loop, always pointing along the circumference in the same direction, you'll see that the fingers are always pointing the same way along the axis of the loop. That is, the contributions all reinforce and concentrate on the inside. Much the same happens on the outside as well so as to give the distinctive Solenoid field pattern, but on the outside the contributions are spread over a wider area, so the concentrating effect is not as great.