A capacitor of 10 microfarads is charged to 12 V. Using U_E = (1/2) C V^2, how much energy is stored in the capacitor?

1. U_E = (1/2) C V^2 = (1/2)(10 x 10^-6 F)(12 V)^2. 2. (12 V)^2 = 144 V^2, so U_E = (1/2)(10 x 10^-6 F)(144 V^2) = 7.2 x 10^-4 J. 3. Converting to millijoules gives 0.72 mJ. 4. Forgetting the one-half factor in the energy formula, as in option A, roughly doubles the true stored energy. _Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.5 Capacitors and Dielectrics_