# Steady state of inductors and capacitors

1. Jul 5, 2014

### ranju

First of all..I want to be clear about steady state..what actually it means..?? Does it mean state of constant current flowing across..?:grumpy:
In my book..its written that in steady state current in inductor and voltage in capacitor is zero , hence energy consumed is zero fotr both in steady state..!!!!!
How come this happens... we know that in steady state of iinductor..voltage across it is zero & that in capacitor at constant voltage across it..cureent through it is zero...!!
Are'nt the two statements contrasting each other..??
plzz explain clearly....

2. Jul 6, 2014

3. Jul 6, 2014

### ranju

yeah,,,its exactly what I stated..
well why the energy is zero in steady state dc in both??? and what about the definition of steady state???

4. Jul 6, 2014

### ranju

and is it compulsory that in steady state the energy stored by a capacitor is zero...??? Because I'hv gone through a question in which the energy stored by the capapcitor in steady state has a certain value..!!

5. Jul 6, 2014

### elegysix

as a simple definition of steady state it just means that voltages and currents aren't changing. energy dissipated is zero for the inductor because there is no voltage across it. Recall P = iV. For the capacitor, there is no energy being dissipated because there is no current.

However, this should not be confused with the energy stored in the magnetic field of the inductor, or the energy stored in the electric field of the capacitor. Those are energies stored by creating the fields, 'building up' after the DC is switched on, but before the circuit reaches steady state.

6. Jul 6, 2014

### ranju

well..is it necesaary that in steady stete both are constant(current n coltage)..even if one is sonstant and other is changing ..will the system be in steady state then?

7. Jul 6, 2014

### Staff: Mentor

You are talking about DC circuits? The steady-state will be reached when all currents and voltages are unchanging with time.