A cylinder wire of radius R is carrying uniformly distributed current I over its cross-section. If a circular loop of radius r is taken as amperian loop, then the variation value of `oint vec(B)* vec(dl)` over this loop with radius 'r' of loop will be best represented by

Options

A.
B.
C.
D.

Answer

B

Explanation

Current within radius `r lt R`:
`I_(i n)=Ipir^(2)=i/(piR^(2))pir^(2)=(ir^(2))/(R^(2))`
For `r lt R, ointvec(B).vec(dl)=mu_(0)I_(i n)=(mu_(0)Ir^(2))/(R^(2)) implies` Parabolic
for `r gt R, ointvec(B).vec(dl)=mu_(0)I_(i n)=mu_(0)I implies` Constant