# Current formula question

1. May 4, 2008

### complexc25

I know I(t) = Io [1 - e-t/t ] is the formula to calculate the current in an RL circuit, however i have no clue what "e" stands for. Can someone give me an insight?

2. May 4, 2008

### Mapes

e is the "en.wikipedia.org/wiki/Exponential_function"[/URL]: here, it means $\mathrm{exp}(-t/\tau)$, where $t$ is time and $\tau$ is a characteristic time constant.

Last edited by a moderator: Apr 23, 2017