Chapter 21, Problem 64P

You measure the electric field strength at points directly above the center of a square plate carrying charge spread uniformly over its surface. The data are tabulated in the next column, with x the perpendicular distance from the center of the plate. Use the data to determine (a) the total charge on the plate and (b) the plate’s size. Hint: You’ll need to consider separately data taken close to the plate and also far away. For the latter, plot E versus a quantity that should yield a straight line.

x(cm)	0.01	0.01	1.2	6.0	12.0	24.0	480.	72.0	96.0	120	240
E(N/C)	5870	5860	4840	1960	754	221	57.6	26.7	16.1	8.45	2.34