Magnetic Circuits

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 ....

\(B=\mu H \)

where H is the mmf per unit length

and hence

\(B=\mu \frac{NI}{l}\)

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.

I didn't realise the airgap length was.. well length. thanks