Determine the magnetic flux:
A coil is wound uniformly with 300 turns over a steel ring of relative permeability 900, with a mean circumference of 40mm and cross-sectional area of 50 mm2. If a current of 25A is passed through the coil, determine (a) m.m.f, (b) reluctance of the ring, and (c) flux.
Solution
(a) Coil m.m.f = NI AT = 300 × 25 = 7500 AT.
(b) Reluctance of the ring = l/ μ0 μr A = (40 × 10- 3)/ (4π× 10 - 7 × 900 × 50 × 10- 6)
= 0.707 ×106 AT/Wb.
(c) Flux = m.m.f/ reluctance = 7500 / (0.707 × 106)
= 10.6 m Wb .