USAP Science Practice Exam

ε0 is the permittivity of free space, the constant that sets how electric fields behave in vacuum. It tells you how much electric field is produced by a given charge in empty space and appears directly in Coulomb’s law through the factor 1/(4π ε0), which governs the strength of electrostatic forces between charges. In vacuum, the electric displacement D relates to the electric field E by D = ε0 E, so ε0 links the field to how the space responds to it. This constant also connects electric and magnetic phenomena: the speed of light c satisfies c^2 = 1/(μ0 ε0), tying ε0 to μ0, the permeability of free space, and showing how electromagnetic waves propagate in vacuum. The value is about 8.854 × 10^-12 farads per meter (F/m). The other options describe different concepts: permeability of free space is μ0, not ε0; electrical conductivity of air is a material property that varies with conditions; and electrical resistance of vacuum isn’t a standard constant (the relevant vacuum property is the impedance of free space, Z0, not a resistance).