2.(adapted from Prob. 3, p. 127, Brown's Introductory Physics If)Now let's assume a charge-q at both positions ta on the axis and a charge +2g at the origin (see Figure

2 above).This is the usual setup that physicists use for spherical coordinates. With x and z as marked, the y axis points in and out of the page, so our whole picture is in the y 0 plane. But since we are writing things in terms of r and 0, you really don't need to worry about x or y or z at all in this problem. If you want more background on spherical coordinates, check out Spherical coordinate c system on Wikipedia. (a)Write an expression for the electric potential of the system at an arbitrary position (r, 0). (b)Is your result positive, negative, or zero at a point on the z axis a distance a above the top charge (where r= 2a and 0 = 0)? How about for a point on the x axis a distance a from the middle charge (where r = a and 0-a/2)? Docs it matter whether the point is to the right or left of the charges? (c)Expand your answer to (a) for r>a, keeping only the largest term that does not cancel. What might we call this system? (Hint: Count the g's. We sometimes call a single point charge a monopole,and a system with two q's (one positive and one negative) is a dipole.)