# 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 = (μo/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 = (μo/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 = (μo/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 = (μo/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

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