# Circuit Problem: Stored Energy

1. Dec 14, 2008

### ACE_99

1. The problem statement, all variables and given/known data
We are given: R1= 1$$\Omega$$
R2= 2$$\Omega$$
L = 3 mH
C = 500 $$\mu$$F

If the voltage is kept at 4V what is the energy stored in the circuit after it has reached a steady state. There is a link posted to the circuit provided below.

2. Relevant equations
energy stored in capacitor = 1/2Cv2
energy stored in inductor = 1/2Li2

3. The attempt at a solution

Since you are given all the values you can just plug into the formula to find the energy stored in the capacitor. I got 0.004J. For the inductor I determined the current that flows through it which is 4V / 2$$\Omega$$ = 2A. I then used this value to compute the energy stored in the inductor, for that I got 0.006J. The total energy would be the sum of the two.

This seems to be a simple problem but I'm just wondering if its a trick question since they want to know what the energy stored is after a long period of time.

2. Dec 14, 2008

### Phrak

The energies (1/2)Li^2 and (1/2)Cv^2 are the steady state values for stored energy. You're result looks correct to me.

3. Dec 14, 2008

### ACE_99

Great thanks.

4. Dec 15, 2008

### CEL

Steady state means after an infinite time. Generally we consider that after 5 time constants the circuit reaches steady state. That is the meaning of a long period of time