R = 120 Ohms.
C = 40 uF = 40*10^-6 Farads.
RC = 120 * 40*10^-6 = 4.8*10^-3 seconds
t/RC = t/4.8*10^-3 = 208.3t
1/e^208.3t = 0.25
e^208.3t = 4
208.3t*Ln e = Ln 4
208.3t = 1.386
t = 0.00666 s. = 6.66 Milliseconds
A charged capacitor, C = 40 micro F, is connected to a resistor, 120 ohms. How much time will elapse until the voltage falls to 25% of its original (max) value?
im not even sure what equation to use for this, so if someone could help me to figure that out it wou
ld be greatly appreciated!
1 answer