As shown in the figure, a long straight conductor with semicircular arc of radius \( \frac{\pi}{10} \, \text{m} \) is carrying current \( I = 3 \, \text{A} \). The magnitude of the magnetic field, at the centre O of the arc is:
(The permeability of the vacuum \( = 4\pi \times 10^{-7} \, \text{N A}^{-2} \).)
