Answer:

Correct option is B)

Given: Magnetic field= 12mT

Solution: The magnetic field due to the straight conductor carrying current is given by,

B=

2πr

μ

0

i

where, i is the current,

r is the distance from the axis and

μ

0

is the permeability constant.

i=

μ

0

2πrB

=

4π×10

−7

2π×2×10

−2

×12×10

−3