Question #122631

An air-gap between two pole pieces is 20 mm in length and the area of the flux path across the gap is 5 cm2. If the flux required in the air-gap is 0.75 mWb. Find the mmf necessary.

Expert's answer

Given

An air-gap between two pole pieces is 20 mm in length ,

A = 5 cm^{2} which is 5*10^{-4} m^{2}

Air gap then = 0.75 mwb = 0.75*10^{-3}

Solution

we know that *B* = *u*_{o}*H*

m.m.f = H*L

but *H* = (alpha/A*u*_{o}) * L and *U*_{o} = 4*3.14*10^{-7}

=(0.75*10^{-3}* 20*10^{-3})/(5*10^{-4 }* 4 *3.14 * 10^{-7})

= 0.238*10^{5} A

Therefore m.m.f = 23870 A

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