RESISTIVITY: ITS EFFECT AND APPLICATION

TABLE OF CONTENT

CONTENTS                                                                 PAGE

Title Page    –        –        –        –        –        –        –        –        i

Certification         –        –        –        –        –        –        –        ii

Dedication –        –        –        –        –        –        –        –        iii

Acknowledgements        –        –        –        –        –        –        iv

Table of Contents –        –        –        –        –        –        –        vi

CHAPTER ONE

1.            INTRODUCTION       –        –        –        –        –        1

CHAPTER TWO

•           THEORY OF RESISTIVITY         –        –        –        –        4
  •      Causes of Resistivity     –        –        –        –        –        7
    • Band Theory simplified –        –        –        –        –        7
    • Metal –        –        –        –        –        –        –        –        8
    • Semi – conductors and insulators     –        –        –        10
    • Ionic liquid/electrolytes  –        –        –        –        –        11
    • Super conductivity        –        –        –        –        –        –        12
  •      Resistivity and conductivity of various materials          –        14

CHAPTER THREE

•      COMPLEX RESISTIVITY AND CONDUCTIVITY          17
  •      Resistivity – density product  –        –        –        –        18
  •      Application of Resistivity       –        –        –        –        20

CHAPTER FOUR

• SUMMARY, CONCLUSION AND REFERENCES 24
  •           Summary and Conclusion       –        –        –        –        24

References

CHAPTER ONE

1.0     INTRODUCTION

Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. Its inverse, called electrical conductivity, quantifies how well a material conducts electricity. A low resistivity indicates a material that readily allows electric current. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm-meter (Ω⋅m) (Lowerie, 2007; Kumar, 2003; Bogattin, 2004). For example, if a 1 m solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity of the material is 1 Ωm (Kumar, 2003).

Electrical conductivity or specific conductance is the reciprocal of electrical resistivity. It represents a material’s ability to conduct electric current. It is commonly signified by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) and γ (gamma) are sometimes used. The SI unit of electrical conductivity is siemens per metre (S/m).

Both resistance and resistivity describe how difficult it is to make electrical current flow through a material, but unlike resistance, resistivity is an intrinsic property. This means that all pure copper wires (which have not been subjected to distortion of their crystalline structure etc.), irrespective of their shape and size, have the same resistivity, but a long, thin copper wire has a much larger resistance than a thick, short copper wire. Every material has its own characteristic resistivity. For example, rubber has a far larger resistivity than copper.

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