hi, i have a question which i was hoping someone could help with, a series circuit featuring a capacitor (C) charging via a 1Mohm (R) resistor and a 12volt dc supply(VS). i know the equation to describe VC is VC=VS(1-e -t/RC) the question is: assuming VC is 2V after a time of 4 seconds, determine approximate value of the capacitor. i have rearranged the equation to C= -t / Rloge(1-VC/VS). i have calculated it as follows: 2/12= 0.166, then 1 - 0.166= 0.834. loge0.834= 2.267 1000000 x 2.267 = 2267047 4/2267047 = 0.0000017644uf please could some one help with the calculation. regards matt.