A long straight wire in the horizontal plane carries a current of 50 A in north to south direction. Give the magnitude and direction of B at a point 2.5 m east of the wire

Options

A. `(2mu_(0)I)/(pir)`
B. `(mu_(0)I)/(2pir)`
C. `2/3(mu_(0)I)/(pir)`
D. `3/8(mu_(0)I)/(pir)`

Answer

C

Explanation

Magnetic field at point P,
`B=(mu_(0)I)/(2pir)+(mu_(0)I)/(2pi(3r))`
= `(3mu_(0)I+mu_(0)I)/(6pir)`
= `(4mu_(0)I)/(6pir)=2/3(mu_(0)I)/(pir)`