1. The problem statement, all variables and given/known data In an oscillating circuit, the capacitance is 2 microfarads and the maximum voltage at the clamps is 5V. Find out 1:the maximum energy of the magnetic field. 2:energy of the mag field when the voltage of the capacitor is 3V. 2. Relevant equations 3. The attempt at a solution First I transformed microfarads in farads. 2 microfarads= 2*10^-6 farads. There isn't any mention of resistance, and it is said that it's an oscillating circuit, so i assumed that resistance is 0. If R=0 => (CU^2)/2 = (LI^2)/2 => 2 * 10^-6 * 9 so the energy of the mag field when the voltage is 3V is 10^-6 * 9 The max energy of the magnetic field is 1/2 * CU^2 =10^-6 * 25 I managed to come to these results by using various bits from others problems in my notebook, but i'm pretty sure they're wrong.