Materials Science and Engineering: An Introduction

William D. Callister, Jr. David G. Rethwisch

ISBN #9780471736967

7th Edition

771 Questions

65,043 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

This section provides a comprehensive exploration of the electrical properties of materials. It covers fundamental principles such as Ohm’s law, the nature of electrical conduction through band structures, and the impact of electron mobility and carrier concentration on conductivity. Distinctions between metals, semiconductors, and insulators are drawn based on their electron energy band configurations, while the role of doping in modifying semiconductor performance is emphasized. Dielectric behavior—including capacitance, polarization mechanisms, and the design considerations for capacitor materials—is also discussed. Finally, specialized electrical phenomena such as ferroelectricity and piezoelectricity highlight unique material behaviors that underpin modern electronic devices.

Learning Objectives

Key Concepts

CONCEPT

DEFINITION

Ceramics Fabrication Techniques

The methods and processes used for shaping, forming, and consolidating ceramic materials into final products with desired properties.

Example Problems

Example 1

(a) Compute the electrical conductivity of a $7.0-\mathrm{mm}(0.28 \text { -in. })$ diameter cylindrical sil icon specimen $57 \mathrm{mm}(2.25$ in.) long in which a current of 0.25 A passes in an axial direction. A voltage of $24 \mathrm{V}$ is measured across two probes that are separated by $45 \mathrm{mm}(1.75 \text { in. })$ (b) Compute the resistance over the entire $57 \mathrm{mm}(2.25 \text { in. })$ of the specimen.

Example 2

An aluminum wire $10 \mathrm{m}$ long must experience a voltage drop of less than $1.0 \mathrm{V}$ when a current of 5 A passes through it. Using the data in Table $18.1,$ compute the minimum diameter of the wire.

Example 3

A plain carbon steel wire $3 \mathrm{mm}$ in diameter is to offer a resistance of no more than $20 \Omega$. Using the data in Table 18.1 , compute the maximum wire length.

Example 4

Demonstrate that the two Ohm's law expressions, Equations 18.1 and $18.5,$ are equivalent.

Example 5

(a) Using the data in Table 18.1 , compute the resistance of an aluminum wire $5 \mathrm{mm}$ $(0.20 \text { in. })$ in diameter and $5 \mathrm{m}(200 \text { in. })$ long. (b) What would be the current flow if the potential drop across the ends of the wire is $0.04 \mathrm{V} ?$ (c) What is the current density? (d) What is the magnitude of the electric field across the ends of the wire?