- #1

DrOnline

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## Homework Statement

I'm decent with differential equations for RLC circuits, and I KNOW the stationary current will be zero, but I need help to work it out mathematically, because my maths gets me -2.4A (...)

L: 0.05H

C: 0.04F

R: 3 Ω

U (source) = 1 V

I've got the transient solution: c

_{1}e-

^{10t}+ C

_{2}e

^{-50t}

Known:

i(0+) = 0 (coil prevents instant change in current)

i'(0+) = u/L = 20

Once the capacitor is charged up, it will block the current. In other words, the stationary current will be zero.

## The Attempt at a Solution

So I could simply declare that, on electrical reasoning, but I want to calculate it. The problem is, my calculation is wrong. Something is wrong.

Been banging my head against this for a while, hope somebody can help me out!

Differential equation: L*i'' + R*i' +1/c*i = u'

i''=0, because i'=20

u'=0, because u=1

I call the stationary current A:

L*0 + R*20 + 1/c A = 0

A=-20*R*C= -2.4

What have I done wrong? If I lack information, please let me know.

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