And the solution in my book is like this:
sensitivity= θ/i = 60/30 = 2 deg/mA
I don't understand why it used the angle 60 (the angle between the coil face and the field lines) instead of the angle 30 (the angle between the normal to the coil and the field lines). My book defines sensitivity as:
The sacale deflection per unit current intensity passes through the coil of the galvanometer.
But still I don't understand what is the relation between the angle 60 degrees and the scale deflection, could you explain it for me?