Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-18 GTBL042-Callister-v2 September 13, 2007 13:46

Revised Pages

Questions and Problems • 755

Magnetic Storage

Information storage is accomplished using magnetic materials in both needle-shaped

particulate and thin-film forms.

Superconductivity

Superconductivity has been observed in a number of materials, in which, upon cool-

ing and in the vicinity of absolute zero temperature, the electrical resistivity vanishes.

The superconducting state ceases to exist if temperature, magnetic field, or current

density exceeds the critical value. For type I superconductors, magnetic field exclu-

sion is complete below a critical field, and field penetration is complete onceHCis

exceeded. This penetration is gradual with increasing magnetic field for type II ma-

terials. New complex oxide ceramics are being developed with relatively high critical

temperatures, which allow inexpensive liquid nitrogen to be used as a coolant.

IMPORTANT TERMS AND CONCEPTS

Antiferromagnetism

Bohr magneton

Coercivity

Curie temperature

Diamagnetism

Domain

Ferrimagnetism

Ferrite (ceramic)

Ferromagnetism

Hard magnetic material

Hysteresis

Magnetic field strength

Magnetic flux density

Magnetic induction

Magnetic susceptibility

Magnetization

Paramagnetism

Permeability

Remanence

Saturation magnetization

Soft magnetic material

Superconductivity

REFERENCES

Bozorth, R. M., Ferromagnetism, Wiley-IEEE

Press, New York/Piscataway, NJ, 1993.

Brockman, F. G., “Magnetic Ceramics—A Review

and Status Report,”American Ceramic Soci-

ety Bulletin,Vol. 47, No. 2, February 1968,

pp. 186–194.

Chen, C. W.,Magnetism and Metallurgy of Soft

Magnetic Materials,Dover Publications, New

York, 1986.

Jiles, D.,Introduction to Magnetism and Magnetic

Materials, 2nd edition, CRC Press, Boca Raton,

FL, 1998.

Keffer, F., “The Magnetic Properties of Materials,”

Scientific American,Vol. 217, No. 3, September

1967, pp. 222–234.

Lee, E. W.,Magnetism, An Introductory Survey,

Dover Publications, New York, 1970.

Morrish, A. H.,The Physical Principles of Mag-

netism,Wiley-IEEE Press, New York/Piscat-

away, NJ, 2001.

QUESTIONS AND PROBLEMS

Additional problems and questions for this chapter may be found on both Student and

Instructor Companion Sites atwww.wiley.com/college/callister.

Basic Concepts

18.1A coil of wire 0.25 m long and having 400

turns carries a current of 15 A.

(a)What is the magnitude of the magnetic

field strengthH?

(b)Compute the flux densityBif the coil is

in a vacuum.

(c)Compute the flux density inside a bar of

chromium that is positioned within the

coil. The susceptibility for chromium is

found in Table 18.2.

(d)Compute the magnitude of the magneti-

zationM.