An infinitely long wire carrying current I is along Y-axis such that its one end is at point A(0,b) while the wire extends up to `+oo`. The magnitude of magnetic field strength at point (a,0) is

Options

A. `(mu_(0)I)/(4pia)(1+b/(sqrt(a^(2)+b^(2))))`
B. `(mu_(0)I)/(4pia)(1-b/(sqrt(a^(2)+b^(2))))`
C. `(mu_(0)I)/(4pia)(b/(sqrt(a^(2)+b^(2))))`
D. None of these

Answer

C

Explanation

`B=(mu_(0))/(4pi) (i/a) [sin90^(@)+sin(-theta)]=(mu_(0))/(4pi) (i/a)(1-sintheta)`
`=(mu_(0))/(4pi) (i/a)(1-b/(sqrt(a^(2)+b^(2))))`