A small magnetised needle $P$ placed at point $O$ and the arrow shows the direction of its magnetic moment. The other arrow show different position (and orientation) of another identical magnets $(Q)$. In which configuration system is not in equilibrium

The magnetic potential at a point on the axial line of a bar magnet of dipole moment $M$ is $V$. What is the magnetic potential due to a bar magnet of dipole moment $\frac{M}{4}$ at the same point

Two identical short bar magnets, each having magnetic moment $M,$ are placed a distance of $2d $ apart with axes perpendicular to each other in a horizontal plane. The magnetic induction at a point midway between them is

Figure shows a small magnetised needle $P$ placed at a point $O$. The arrow shows the direction of its magnetic moment. The other arrows show different positions (and orientations of the magnetic moment) of another identical magnetised needle $Q$.

$(a)$ In which configuration the system is not in equilibrium?

$(b)$ In which configuration is the system in $(i)$ stable, and $(ii)$ unstable equilibrium?

$(c)$ Which configuration corresponds to the lowest potential energy among all the configurations shown?

Two identical short bar magnets, each having magnetic moment $M$ are placed a distance of $2d$ apart with axes perpendicular to each other in a horizontal plane. The magnetic induction at a point midway between them is