Capacitance (Question 1 (10 Marks)) — UPSC Physics Optional CSE 2017 Paper I

A current i(t)=(2e^{-t}-e^{-2t})\,\mu\mathrm{A} charges up a 120\,\mathrm{nF} capacitor for a period of 2 seconds. If the final voltage across the capacitor is 15\,\mathrm{V}, what was the initial voltage across it?