Suppose an electric charge p(x, y) is uniformly spread on a disc of radius r around the origin. use maxwell's first equation (in a non-dimensional version) (4) v e = p from the origin r > r, the field is proportional to r-1. that far to prove away do not use the explicit formula for the electric field. do use the fact that the electric field points towards the charged particle, and whatever symmetries this problem has.

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

The passing of heat through a material while the material itself stays in place. a. radiation b. conduction c. convection

The two required components for a generator are