- #1
manenbu
- 103
- 0
Homework Statement
I need to calculate:
[tex]\oint_{\Gamma} \vec{F}\cdot d \vec{r}[/tex]
where:
[tex]
\vec{F} = \frac{-y \vec{i} + x \vec{j}}{x^2+y^2}
[/tex]
where [itex]\Gamma[/itex] is the positive direction circle:
a. x2 + y2 = 1
b. (x-2)2 + y2 = 1
Homework Equations
[tex]\int_{C} \nabla f \cdot d \vec{r} = f(\vec{r}(b)) - f(\vec{r}(a))[/tex]
and/or (??)
[tex]\int_{C} \nabla f \cdot d \vec{r} = \int_{a}^{b} \nabla f (\vec{r}(t)) \cdot \vec{r}'(t) dt [/tex]
The Attempt at a Solution
I'm totally lost on this one.
I found out that [itex]f = -\arctan{\frac{x}{y}}[/itex], and that in polar coords:
[tex]\vec{F} = \left( \frac{-\sin{\theta}}{r} , \frac{\cos{\theta}}{r} \right)[/tex]
But what to do now?
I tried doing the stuff required by the relevant equations but nothing seems to work, for both circles. What am I missing here?
Thanks in advance.