In this
section, we shall take the simple example of two parallel
current- carrying conductors, which will perhaps help us
to appreciate Ampere’s painstaking work Rationalised 2023-24
123
Moving Charges and
Magnetism
Figure 4 17 shows two long parallel conductors a and b separated
by a distance d and carrying (parallel) currents Ia and Ib, respectively The conductor ‘a’ produces,  the same magnetic field Ba at all points
along the conductor ‘b’