A series circuit with a 12kΩ resistor, a 12.0 V battery and a capacitor has a time constant of 55 μs.
a) Compute the capacitance of the circuit?
b) Compute the time it takes for the energy stored in the capacitor to be two thirds of its maximum value?
c) What is the value of j at this time if the wire has a radius of 5.0 mm?