Question

Axis of a solid cylinder of infinite length and radius R lies along y-axis. It carries a uniformly distributed current I along +y direction. Magnetic field at a point `(R//2, y, R//2)` is
A. `(mu_(0)I)/(4 pi R) (hat(i)-hat(k))`
B. `(mu_(0)I)/(2 pi R) (hat(j)-hat(k))`
C. `(mu_(0)I)/(4 pi R) hat(j)`
D. `(mu_(0)I)/(4 pi R) (hat(i)+hat(k))`

Answer 1

Correct Answer - A
`r=Rsqrt(2),(B)=(mu_(0)I(R//sqrt(2)))/(2piR^(2))=(mu_(0)I)/(2sqrt(2)piR)`
`vecB=B[cos45^(@)hati+sin45^(@)(khatk)]=(mu_(0)I)/(4piR)[hati-hatk]`