For line integrals in vector calculus, [tex]\int^a_b F \cdot dl[/tex] I almost always see the path oriented from a to b. But my text book has the following (look at the first equation for V(r): Since the integral's limits are from O to r, I would have expected dl to also be pointing in the direction from O to r (i.e. pointing in the radially inward (minus r hat) direction), but the math in the textbook seems to imply that dl points radially outward (positive r hat direction, from r to O). I say this because the result of E dot dl has no minus sign in front of it. How do you know which direction to orient dl?