Part 1: (RC circuit) 5 identical resistors with resistance R are connected in series, while 5 identical capacitors with capacitance C are connected in parallel. The internal resistance of the battery is negligible. What is the time constant of this RC circuit (in term of RC)?
Part 2: (Charging a capacitor) An uncharged 10-microF capacitor and a 100 kOhm resistor are connected in series, and 100 V is applied across the combination. How long (in unit of seconds) does it take for the capacitor voltage to reach 80V?