A 25 micro farad is charged until the potential difference across it is 500V. Calculate the charge stored at this moment.

The formula to be used here is C = Q / V. Where C = capacitance, Q = charge and V = potential difference. First we can put in the values to get 25 * 10^-6 = Q / 500. This can be rearranged to Q = 500 * 25 * 10^-6. This multiplies to 1.25 * 10^-2 C.