Question

A circuit with a capacitor took .128s to discharge from its max charge Qmax to half of that max charge once the battery was removed. In this series circuit there also is one resistor with 100 G(ohm symbol). The voltage drop is 12V across the battery.

What is the time constant of this circuit?

I know that time constant = RC but we are given two unknowns the time constant and the capacitance. R would be 100 x 10^9 or 1 x 10^11.

Answer 1

1/2=e^(-t/rc)

Is this the problem statement?
Solve for c.