Please answer material science 8. Magnetic Material (Chapter 8) An inductive hea

Question

Please answer material science 8. Magnetic Material (Chapter 8) An inductive head can be modeled as a permalloy core with a gap in it. Permalloy core with .-10,000 Coil with 50 turns Total Length of core L-100 Length of gap Ls = 0.2 A) Given the above geometry, derive the field at the gap Hgap as a function of coil current. Assume the permalloy is a soft magnetic material so that hysteresis can be modeled as linear until it saturates. B) If the saturation induction (Buat) of permalloy is I [T], what is the maximum field Hep that can be achieved? C) What coil current is required to achieve this maximum field? D) It is possible to use this head for reading a hard drive as well as writing. If the disk is spinning at 10,000 rpm, the disk radius is 5cm, the bit length is 0.2 microns, and the maximum field emanating from each bit is 1000 A/m, estimate the readback voltage that the head produces. The cross-sectional area of the gap in the head is 2 x 10-12 m2

Explanation / Answer

(A) For a coil of wire,

H = I x N/L

Where H=Strength of magnetic field in Amp-Turns/Mtr

N=Number of turns

I= Current flowing through the coil in Amps

L=Length of the coil in Mtrs.

(B) For practical purposes, B and H are related by

B=µ0 µr H

We have been given with value of B & µr and value of µ0 is 410-7. By substituting these values wee get

Hgap=7.95 AT/M.

(C) The current required to achieve this field is

I =H x L / N = 0.0318 µA

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