Two flat rectangular plates form a capacitor (Figure). A dielectric plate can move between them without friction, the thickness of which coincides with the gap between the plates h, and the width is equal to b (not shown in the figure). The emf of the source and the dielectric constant of the plate material e are also known. What power does the battery expend at the moment when the dielectric is drawn into the capacitor at an instantaneous speed v? How is this power distributed between mechanical and electrical?

Answer. Format gif