# Problem in auto induction .

## Homework Statement

i tried to put all data in the image .

http://img136.imageshack.us/img136/7443/photokg6.th.jpg [Broken]

in the initial situation K was closed.in T = 0 ,K was opened.

give the differenciel equation of the courant.

## The Attempt at a Solution

(R+r)*i + L (di)/(dt) = 0 .

my problem is that i don't know if we have to put (R+r)*i or only r*i in the differentiel equation of the courant .

thanks in advance for any help.

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