What causes the couple acting on the needle of a compass?

The length of a steel wire is $L$ and its magnetic moment is $M$. On bending it into the shape of a semicircle,its magnetic moment will be

$A$ rod of length $5 \, cm$ and diameter $1 \, cm$ has a magnetization of $5.30 \times 10^3 \, A/m$. What is its magnetic moment?

$A$ metal wire of length $l$ has a magnetic moment $M$. What is the new magnetic moment if it is bent into an $L$-shape?

$A$ permanent magnet:

The magnetic dipole moment of a short magnetic dipole at a distant point along the equator of the magnet has a magnitude of $X$ in $SI$ units. If the distance between the point and the magnet is halved,then the magnitude of the dipole moment will be