a current of 10 A is flowing east to west in a long wire kept horizontally in east west direction. find magnetic field and its direction in the horizontal plane at a distance of

(i)10 cm north

(ii) 20 cm south from the wire.

and in the verical plane at a distance of

(i)40 cm downward

(ii)50 cm upward.

Here,

Horizontal plane

I = 10 A

r = 10 cm

  = 0.1 m

Towards north

For straight wire

B = (μ_o/4π)2I/r

=>  B = 10^-7×2×10/0.1

=> B = 2×10^-5T

Direction of magnetic field will be downwards the horizontal plane of paper

I = 10 A

r = 20 cm

  = 0.2 m

Towards south

For straight wire

B = (μ_o/4π)2I/r

=>  B = 10^-7×2×10/0.2

=> B =  T

Direction of magnetic field will be upwards the plane of paper

Here,

Vertical plane

I = 10 A

r = 40 cm

  = 0.4 m

For straight wire

B = (μ_o/4π)2I/r

=>  B = 10^-7×2×10/0.4

=> B = 5×10^-5T

Direction of magnetic field will be inside the plane of paper

I = 10 A

r = 50 cm

  = 0.5 m

For straight wire

B = (μ_o/4π)2I/r

=>  B = 10^-7×2×10/0.5

=> B = 4×10^-6T

Direction of magnetic field will be towards outside the plane of paper