Why do iron filings arrange themselves in a certain pattern around a magnet?

$A$ straight conductor passes vertically through a cardboard sprinkled with iron filings. Show the setting of iron filings when a weak current is passed in the downward direction and then the cardboard is gently tapped. Draw arrows to represent the direction of magnetic field lines.
What changes occur if,
$(i)$ the strength of current is increased?
$(ii)$ the single conductor is replaced by several parallel conductors each carrying same current flowing in the same direction?

In the below figure,$A$ and $B$ represent two straight wires carrying equal currents in a direction at right angles to the plane of paper inwards. Sketch separately the magnetic field lines produced by each current. Give a reason why the magnetic field at $K$ (mid-point of the line joining $A$ and $B$) will be zero.
What will be the effect on the magnetic field at $K$ if the current in wire $B$ is reversed?

How is the relative strength of a magnetic field shown around a magnet?

According to the Right-Hand Thumb Rule,what does the thumb indicate?

How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire?