The equation governing the amount of current I (in amperes) after time t (in seconds) in a simple RL circuit consisting of a resistance R (in ohms), an inductance L (in henrys) and an electromotive force E (in volts) is given by
I = (E/R)[1 - e^(-(R/L))t]
If E = 12 volts, R = 10 ohms and L = 5 henrys, how long does it take to obtain a current of 0.5 ampere?
Aug 4th 2008, 03:49 AM
Originally Posted by Air
Rearrange to make time the subject and then substitute the values give.
Rearranging the equation for time, I obtained:
Unfortunately Air, despite appearances to the contrary, the expression is meant to be .
Since my algebra is terrible, I'd substitute the given values first and then re-arrange. I find it much easier to manipulate concrete numbers.
Do this and you should be able to get to
From here the path leading to t shouldn't be too slippery.