Line Integral Vector function

Line Integral of Vector Function

You can consider the integral of a vector function F along a curve C. The vector function F has the components [image] and [image]. The path of the parameterized function is [image].

 

The parameter t reaches from a to b.

 

If you use this vector function then the differential d naturally is dr.

 

[image]

 

This formular expresses that there is a tangent component t of F along the path.

 

[image]

 

The trajectory of a particle r along a curve (the path C) inside a vector field (Source: Lucas V. Barbosa)

 

 

Now the distance gets the name ds.

 

[image]

 

[image]

The line integral over a scalar field f is the area under the curve C along a surface z = f(x,y) which is described by the field (Source: Lucas V. Barbosa)

 

The line integral is also equivalent to:

 

[image]

 

 

[image]  Example

 

Evaluate the line integral for the function [image] for [image]. The path shall be a straigt line [image].

 

First, write down a parametric function for the path.

 

[image]

 

t is from 0 to 1.

 

The new parameters are:

 

[image]

 

The derivative of x is [image]

 

[image]

 

The derivative of y is [image]

 

 

Put in these parameters into the function F for each dimension x and y.

 

First dimension x: [image]

 

The term [image] is filled in with [image] and the term [image] is filled in with [image]

 

[image]

 

Second dimension y: [image]

 

The term [image] is filled in with [image] 

 

[image]

 

Put in the parameterized variables in an integral.

[image]

 

[image]