Posted by adam h. on .
Two capacitors are identical, except that one is empty and the other is filled with a dielectric (k = 4.5). The empty capacitor is connected to a 15 V battery. What must be the potential difference across the plates of the capacitor filled with a dielectric so that it stores the same amount of electrical energy as the empty capacitor?

physics 
bobpursley,
energy=1/2 C v^2
so v=sqrt(1/k)
check that.