A toroid with thick windings of $$N$$ turns has inner and outer radii $$R_1$$ and $$R_2$$, respectively. If it carries certain steady current $$I$$, the variation of the magnetic field due to the toroid with radial distance is correctly graphed in

A tightly wound long solenoid has $n$ turns per unit length, a radius $$r$$ and carries a current $$I$$. A particle having charge $$q$$ and mass $$m$$ is projected from a point on the axis in a direction perpendicular to the axis. The maximum speed of the particle for which the particle does not strike the solenoid is

Which of the field pattern given below is valid for electric field as well as for magnetic field?

In the given figure, the magnetic field at $$O$$.