AP EAMCET202119 Aug 2021Morning ShiftPhysicsMagnetic Effects of CurrentActual
A long thin hollow metallic cylinder of radius R has a current i ampere. The magnetic induction B away from the axis at a distance ' r ' from the axis varies as shown in
Options
- Ai
- Bi i
- Ci i i
- Di v
Correct answer
A. i
Step-by-step solution
Using ampere circuital law, ∮ B → · d l → = μ 0 I If an ampere loop is taken inside the hollow cylinder then, ∮ B → · d l → = μ 0 × 0 = 0 If an ampere loop is taken of radius r   such that r ≥ R   then, ∮ B → · d l → = μ 0 I B 2 πr = μ 0 I B = μ 0 I 2 πr As it can be clearly seen that there is no magnetic field inside the hollow cylindrical metal and outside the cylinder B ∝ 1 r