electrostatics.py 文件源码

def E(self, x):  # pylint: disable=invalid-name
        """Electric field vector.
        Ref: http://www.phys.uri.edu/gerhard/PHY204/tsl31.pdf
        """
        x = array(x)
        x1, x2, lam = self.x1, self.x2, self.lam

        # Get lengths and angles for the different triangles
        theta1, theta2 = angle(x, x1, x2), pi - angle(x, x2, x1)
        a = point_line_distance(x, x1, x2)
        r1, r2 = norm(x - x1), norm(x - x2)

        # Calculate the parallel and perpendicular components
        sign = where(is_left(x, x1, x2), 1, -1)

        # pylint: disable=invalid-name
        Epara = lam*(1/r2-1/r1)
        Eperp = -sign*lam*(cos(theta2)-cos(theta1))/where(a == 0, infty, a)

        # Transform into the coordinate space and return
        dx = x2 - x1

        if len(x.shape) == 2:
            Epara = Epara[::, newaxis]
            Eperp = Eperp[::, newaxis]

        return Eperp * (array([-dx[1], dx[0]])/norm(dx)) + Epara * (dx/norm(dx))