An electromagnetic actuator has 2 iron poles with 5mm airgap between them. Each pole has an area of 15 cm^2. A coil of 100 turns is used to create a flux density of 1.2T in the airgap. Assume core has infinite permeability. Calculate the required coil current. So far I have the flux(phi) = B*A = 1.2 x 1.5 x 10^-3 = 1.8x10^03. Then from there I'm not sure where to go.
You don't really need to calculate the flux. Do you know the relationship .... where H is the mmf per unit length and hence You are given B, N & l - the air gap length. All the applied mmf is taken up in the air gap. You need to decide on a value for μ. From there the only unknown is I, which is what you require.