An air-filled parallel-plate capacitor is connected to a battery and allowed to charge up. Now a slab of dielectric material is placed between the plates of the capacitor while the capacitor is still connected to the battery. After this is done, we find that the charge on the capacitor had increased. the energy stored in the capacitor had decreased. the voltage across the capacitor had increased. the charge on the capacitor had not changed. None of these choice are true.