A steady current `I` flows along an infinitely long hollow cylindrical conductor of radius `R`. This cylinder is placed coaxially inside an infinite solenoid of radius `2 R`. The solenoid has a `n` turns per unit length and carries a steady current `I`. Consider a point `p` at a distance `r` from the common axis . The correct statement(s) is (are)

Options

A. In the region `0 lt r lt R`, the magnetic field is non-zero
B. In the region `R lt r lt 2R,` the magnetic field is along the common axis.
C. In the region `R lt r lt 2R,` the magnetic field is tangential to the circle of radius r, centred on the axis.
D. In the region `r gt 2R`, the magnetic field in non-zero.

Answer

A, D

Explanation

(a,d): Due to field of solenoid is non zero in region `0 lt r lt R` and
non zero in region `r gt 2R` due to conductor.