10. In moving four times as far away from a cyrrent-carrying conductor, the density of the flux lines will have __ by FOPUfour times.

The magnetic field strength (and thus the flux density) around a long, straight, current-carrying conductor is inversely proportional to the distance from the conductor. This relationship is described by Ampere's Law and, for a long straight wire, results in the equation:B = (μ₀ * I) / (2π * r)Where:* B is the magnetic field strength (or flux density)* μ₀ is the permeability of free space (a constant)* I is the current* r is the radial distance from the wireIf the distance (r) is increased by a factor of four (i.e., quadrupled), the magnetic field strength (B) will decrease by a factor of four.Therefore, the density of the flux lines will **decrease** by four times.