What change is observed in the deflection of the compass needle placed at a point near a straight current-carrying conductor if the
a] current through the conductor is increased ?
b] direction of current in the conductor is reversed ?
c] compass is moved away from the conductor ?

Explanation

a] The deflection of the compass needle increases because of the increase in the strength of the magnetic field [B `prop` l]
b] The direction of deflection of the compass needle is reversed because the direction of magnetic field is reversed.
c] The deflection on the compass needle decreases due to the decrease in the strength of the magnetic field [B `prop` 1/r].