$(a)$ An electric current is passed in a horizontal copper wire from east to west. Explain your observations when a compass needle is placed $(i)$ below this wire,$(ii)$ above the wire. Draw inference from your observations.
$(b)$ List the factors on which the strength of the magnetic field due to a straight conductor carrying current depend. How should these be changed to decrease magnetic field at a point?

(A) According to Oersted's experiment and the Right-Hand Thumb Rule,when current flows from east to west,the magnetic field lines form concentric circles around the wire. $(i)$ When the compass is placed below the wire,the north pole of the needle will deflect towards the south. $(ii)$ When the compass is placed above the wire,the north pole of the needle will deflect towards the north. Inference: The direction of the magnetic field depends on the direction of the current and the position of the point relative to the wire.
$(b)$ The strength of the magnetic field $(B)$ due to a straight current-carrying conductor depends on: $(i)$ The magnitude of the electric current $(I)$: $B$ is directly proportional to $I$. $(ii)$ The perpendicular distance $(r)$ from the conductor: $B$ is inversely proportional to $r$. To decrease the magnetic field at a point,one should: $(i)$ Decrease the magnitude of the current flowing through the conductor. $(ii)$ Increase the perpendicular distance of the point from the conductor.