3energy storage consider the capacitor as a device for storing energy. the practical limitation on the potential difference between the plates of a capacitor is the "dielectric strength" of the dielectric material between the plates. this is the maximum field strength that can exist without causing a spark. it is typically on the order of 107 v/m for a good liquid dielectric with k 2.3 and ρ ~: 1 g/cm3 (a) neglecting the weight of the electrodes and case, what is the energy density of the capacitor in j/kg? le., how many joules of energy can be stored per kilogram of dielectric? physics 222 winter 2018 january 21, 2018 (b) the energy density of gasoline is about 46 mj/kg, and gasoline has a density of about 0.75 g/cm3. assume a gas tank holds about 12 gallons when full. what mass of dielectric would be required to provide the same energy as a tank of gasoline?