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Conservative Vector Field





DEFINITION


A vector field \mathbf{v} is said to be ''conservative'' if there exists a scalar field \phi such that

: \mathbf{v}=-
abla\phi.

Here
abla\phi denotes the Gradient of \phi. When the above equation holds, \phi is called a Scalar Potential for \mathbf{v}.


PATH INDEPENDENCE


A key property of a conservative vector field is that its integral along a path depends only on the endpoints of that path, not the particular route taken. Suppose that S\subseteq\mathbb{R}^3
is some region of three-dimensional space, and that P is a path in S with start point A and end point B . If
\mathbf{v}=-
abla\phi is a conservative vector field then

: \int_P \mathbf{v}\cdot d\mathbf{r}=\phi(A)-\phi(B).

This holds as a consequence of the Chain Rule and the Fundamental Theorem Of Calculus .

An equivalent formulation of this is to say that

: \oint \mathbf{v}\cdot d\mathbf{r}=0

for every closed loop in S .

The converse of the above statement is also true. That is, if the Circulation of \mathbf{v} around every closed loop in S is zero, then \mathbf{v} is a conservative vector field.


IRROTATIONAL VECTOR FIELDS


A vector field \mathbf{v} is said to be ''irrotational'' if its Curl is zero. That is, if

:
abla imes\mathbf{v} = 0.

For this reason, such vector fields are sometimes referred to as ''curl-free'' vector fields.

It is an identity of vector calculus that for any scalar field \phi:

:
abla imes
abla \phi=0.

Therefore every conservative vector field is also an irrotational vector field.

Provided that S is a Simply-connected region the converse of this is true: every
irrotational vector field is also a conservative vector field.



where G is the Gravitational Constant and \hat{\mathbf{r}} is a unit vector pointing from M towards m. In this case \mathbf{F}_G=-
abla\phi_G, where

: \phi_G=- rac{GmM}{r}

is the Gravitational Potential .

In the case of Conservative Forces , ''path independence'' can be interpreted to mean that the Work Done in going from a point A to a point B
is independent of the path chosen, and that the work done in going around a closed loop is zero. In other words, the total Energy of a particle moving under the influence of conservative forces is conserved.


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