$(a)$ Explain any three properties of magnetic field lines.
$(b)$ Give two uses of magnetic compass.

(N/A) Properties of magnetic field lines:
$(i)$ Magnetic field lines emerge from the north pole and merge at the south pole outside the magnet.
$(ii)$ They form continuous closed loops.
$(iii)$ The strength of the magnetic field is indicated by the degree of closeness of the field lines; they are stronger where the field lines are crowded.
$(iv)$ No two magnetic field lines can ever intersect each other,as that would imply two directions of the magnetic field at a single point,which is impossible.
$(b)$ Uses of a magnetic compass:
$(i)$ It is used to determine the cardinal directions (North,South,East,West).
$(ii)$ It is used to detect the presence of a magnetic field around a current-carrying conductor or a magnetic material.