V = 240 ( 1 - e -(rt)L )
given R = 1 ohm
given L = 200mH
calculate the time when the voltage is expected to be 140v
been trying for ages just cant crack it
Now substitute the given data into the equation (note that 200mH = 0.2 H):
and I'm sure you can do the finishing touches.
(Since I've worked in SI units the time you get will be measured in seconds).