The magnetic field due to current in a straight wire segment of length L at a point on its perpendicular bisector at a distance `r ( r gt gt L)`

Options

A. decreases as `(1)/(r )`
B. decreases as `(1)/(r^(2))`
C. decreases as `(1)/(r^(3))`
D. approaches a finite limit as `r rarr oo`

Answer

B

Explanation

From Biot-Savart.s law, `dB= (mu_(0))/(4pi) (Idl)/(r^(2))` i.e., `dB prop (1)/(r^(2))`
Hence option (b) is correct.