A parallel-plate capacitor with plate separation \(d\) and air between its plates is connected across an ideal battery of constant potential difference \(\Delta V\). While the capacitor remains connected to the battery, a dielectric slab with dielectric constant \(\kappa > 1\) is slowly inserted until it completely fills the space between the plates. Which of the following correctly describes what happens to the magnitude of the net electric field between the plates and the total electric potential energy stored in the capacitor as a result of inserting the slab?