# How do you differentiate Kirchoffs law?

1. Mar 14, 2013

### Needhelp2013

How do you differentiate kirchoffs law which seems to be I = (R+L(di/dt))/V(t)

I need it to be a differential equation so then I can use eulers method.

2. Mar 14, 2013

### HallsofIvy

?? That ]b]is[/b] a differential equation- it involves di/dt. You shouldn't really need to user Euler's or any numerical method: di/dt= (IV(t)- R)/L which can be integrated. I am assuming i and I are different. If you meant i= (R+ L(di/dt))/V(t) then that can be written as L(di/dt)- V(t)dt+ R= 0. For that, with general functions as coefficients, yes, a numerical method is needed. Is there a reason why you specifically wrote V(t), as a function of t, but not L and R?

3. Mar 14, 2013

### Needhelp2013

This is the question I have been asked in full: A resistor R = 15 ohms an inductor of L=2 henries and a battery of E volts are connected in series with a switch S. At time t=0 the switch is closed and the current I=0. Use Euler Method (Excel or hand but show all work on assignment) to find I at time t =.4 if E=10 and h=.1.

I believe the equation of the circuit to be Vt=IR + L(di/dt).This has then got to be converted into a differential equation so that I can then proceed to use eulers method. Yes i and I are different in the equation.