7.1 Introduction

Line integrals:

• work;
  
  $$\epsffile{lininti.eps}$$
  
  

• potential energy;
• velocity potential
• ...

Path independence:

$$\int_A^B \vec F \cdot {\rm d}\vec r$$

is independent of the path between $A$ and $B$ when $\mbox{curl} \vec F \equiv \mbox{rot} \vec F \equiv \nabla \times \vec F = 0$.