where S_core is the reluctance of the core and S_air is the reluctance of the air gap.

S_air = lg / (μ₀ * A) = 0.0005 / (4π x 10^(-7) x 0.02) = 1989 A/Wb

The magnetic flux is given by:

The MMF is given by:

Φ = MMF / S = 1600 / 5969 = 0.268 Wb

S = 3980 + 1989 = 5969 A/Wb