physics
posted by san juan on .
An RC circuit contains a 3.9 kΩ resistor and a 5 µF capacitor. When the switch is first closed in the circuit, a maximum current of 1.5 mA flows in the circuit. Using Equation (1), find the time at which the current flow will have fallen to 1.0 mA.

Hmmm.
I=V/R e^t/rc is that you equation?
1.0=3.5e^t/rc
take the ln of each side
ln1.0ln3.5=t/RC
solve for time t.