30. A 1.00-F capacitor, initially charged to 12 V, discharges when connected in series with a...

30. •• A 1.00-μF capacitor, initially charged to 12 V, discharges when connected in series with a resistor.

(a) What resistance is necessary to cause the capacitor to have only 37% of its initial charge 1.50 s after starting?

(b) What is the voltage across the capacitor at a time t = 3τ if the capacitor is instead charged by the same battery through the same resistor?