KCET2009PhysicsMagnetic Effects of Current
A direct current I flows along the length of an infinitely long straight thin walled pipe, then the magnetic field is
Options
- Auniform throughout the pipe but not zero
- Bzero only along the axis of the pipe
- Czero at any point inside the pipe
- Dmaximum at the centre and minimum at the edge
Correct answer
C. zero at any point inside the pipe
Step-by-step solution
Required arrangement is shown in figure. According to Ampere's circuital law. For an internal point, r < R B _ internal = ₀(0) 2 r =0 For a point on the pipe, r=R B= ₀ I 2 r For an external point, r < R B _ external = ₀ I 2 r Therefore, option (c) is correct.