A parallel plate capacitor made to circular plates each of radius R = 6cm has capacitance C = 100pF. The capacitance is connected to a 230V A.C. supply with an angular frequency of 300 rad/s.The value of B at a point 3 cm from the axis between the plates will be:

 1.63 x 10^–11T

$ B_0 = \frac{\mu_0 (I_D)_{peak}r}{2\pi R^2} = \frac{2\times 10^{-7} \times \sqrt 2 \times 6.9 \times 10^{-6}\times 3\times 10^{-2}}{36\times 10^{-4}} =1.63\times 10^{-11}T$