Positive charge Q is uniformly distributed around a semicircle of radius a as shown in Fig. 21.34. Find the magnitude and direction of the resulting electric field at point P, the center of curvature of the semicircle. SOLUTION GUIDE IDENTIFY and SET UP 1. The target variables are the components of the electric field at P. 2. Divide the semicircle into infinitesimal segments, each of which is a short circular arc of radius a and angle de. What is the length of such a segment? How much charge is on a segment? 21.34 Charge uniformly distributed around a semicircle. P 3. Consider an infinitesimal segment located at an angular position 0 on the semicircle, measured from the lower right corner of the semicircle at x = a , y = 0. (Thus 0 = T/2 at x = 0, y - a and 0 = n at x = - a, y = 0.) What are the x- and y-components of the electric field at P (dEx and dEy) produced by just this segment?