31. Image Charge II Consider a point charge Q at a distance d from the center of a conducting, grounded (V = 0) sphere. In order to determine the resulting electric field, it is possible to replace the sphere with an image charge (' at a distance a from the center (see Fig. 2). V=0 R Q' Q d Figure 2: Charge Q in front of conducting, grounded sphere. (a) Find the position a and the charge Q' of the image charge. (b) Determine the force that acts on the point charge