A permanent magnet moving coil instrument has a coil of dimension $$10 mm \times 20 mm$$. The flux density in the air gap is $$2 \times 10^{-3} Wb/m^2$$ and the spring constant is $$0.25 \times 10^{-6} Nm/rad$$. If the current of 10 mA is  flowing through the coil, then calculate the number of turns required to produce an angular deflection of 60 degrees.

A

50

B

55

C

60

D

65