Halliday, Resnick & Walker — Gauss' Law: Problem 45

45 The square surface shown in Fig. 23-44 measures 6.8 mm on each side. It is immersed in a uniform electric field with magnitude $E = 1800 \text{ N/C}$ and with field lines at an angle of $\theta = 35^\circ$ with a normal to the surface, as shown. Take that normal to be directed “outward,” as though the surface were one face of a box. (a) Calculate the electric flux through the surface. (b) If the angle is reduced by a few degrees, does the flux increase, decrease, or remain the same?