A hollow, right circular cone of base radius $$R$$ and height $$h$$, with its tip at the origin is rotating about the $$Z$$-axis with an angular velocity $$\omega$$, as shown in the figure. The cone carries a total charge $$Q$$ uniformly distributed on its curved surface. The magnitude of magnetic field at a point $$(0,0,z)$$, where $$z\gg R$$ and $$z\gg h$$, is $$\dfrac{n\mu_0}{4\pi}\dfrac{QR^2\omega}{z^3}$$. The value of $$n$$ is: