JEE Advanced2013PhysicsMagnetic Effects of CurrentActual
A steady current I flows along an infinitely long hollow cylindrical conductor of radius R . This cylinder is placed co-axially inside an infinite solenoid of radius 2 R . The solenoid has 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
- AIn the region 0 < r < R , the magnetic field is non-zero.
- BIn the region R < r < 2 R , the magnetic field is along the common axis.
- CIn the region R < r < 2 R , the magnetic field is tangential to the circle of radius r , centered on t
- DIn the region r > 2 R , the magnetic field is non-zero.
Correct answer
A. In the region 0 < r < R , the magnetic field is non-zero.
Step-by-step solution
If we consider a point at a distance r from a common axis such that 0 < r < R , the magnetic field is non-zero because inside infinite solenoid magnetic field is, B →   =   μ 0 n i and due to the hollow cylinder it is zero. Hence, net magnetic field is non-zero. If 2 R < r , then magnetic field due to an infinite solenoid is zero but there will be a non-zero magnetic field because of hollow cylinder. Hence, net magnetic field is non-zero. If R < r < 2 R , then the magnetic f