12. (10 points) An empty (means vacuum, k = 1) parallel plate capacitor is connected to a 12 V battery. The distance between the two plates is 12.0 cm. As shown in the figure below (not to scale), Line BC (AC) is parallel (perpendicular) to the electric field lines. AC = 1.5 cm, BC = 2.0 cm. (1) A point charge (-2 MC) is moved from point A to point B. During this process, Does the electric potential energy of the point charge increase or decrease? What is the magnitude of the change? (2) If the same point charge (-2 MC) is moved from point A to point C and then point B (the initial and final positions are the same). Compared to the path in (1), does the work done on the point charge increase or decrease, or being the same? Is the work positive or negative? (3) The capacitor is disconnected from the battery, and a dielectric material with K = 2 is inserted into the capacitor. If the same point charge (-2 HC) is moved from point A to point B. Calculate the change of the electric potential energy of the point charge. Don't forget the sign. + + +9 -9 BO