Answer:
46.80 m
Explanation:
Given:
Magnetic field, B = 2.6 kG = 2600 G = 0.26T
Diameter of the plastic tube = 12 cm = 0.12m
Length of the plastic tube = 60 cm
Current, I = 2 A
The formula for the magnetic field (B) at the center of a solenoid is calculated as:

where,
I = current
N = Turns
L = Length
= permeability of the free space
on substituting the values in the above equation, we get

or
N = 62070.42 Turns
also, each turn is a circumference of the plastic tube.
The circumference of the plastic tube, C = 2π×0.12 = 0.7539 m
Thus,
The total length of the wire required, L = (62070.42) × 0.7539 m = 46799.99 ≈ 46800 m = 46.80 km