# Complex circuit problem

#### jdverbek

Joined Aug 31, 2023
3
I have a question regarding a problem I encountered during exercises. In geometrically “unconventional” circuits (at least to me) I often find myself unable to see whether components are truly in series or parallel, and how I should approach the problem. Mostly it is because of a weird location of a source (in a bridge, in one of the limbs of a delta/wye etc.). Consider the diagram below, where the open circuit voltage Vok should be determined.

Can someone help me with this? Not just the answer, but especially the reasoning behind the approach please.

#### Alec_t

Joined Sep 17, 2013
14,009
Welcome to AAC!
1) Is E an AC source or a DC source?
2) Do the inductors have inherent resistance?
3) Do the resistors have inherent inductance?

#### jdverbek

Joined Aug 31, 2023
3
In the question, E was indeed an AC source (I know in DC the inductors behave as short-circuits).

#### ericgibbs

Joined Jan 29, 2010
18,234
hi,
Does this redraw look more familiar to you?
E

#### jdverbek

Joined Aug 31, 2023
3
Yes, that looks like something I can handle! But how do I see I can redraw it like that?

#### MrAl

Joined Jun 17, 2014
10,909
Yes, that looks like something I can handle! But how do I see I can redraw it like that?
Hi,

Start by rotating all the components except the source until they are vertical instead of horizontal.

#### WBahn

Joined Mar 31, 2012
29,512
I have a question regarding a problem I encountered during exercises. In geometrically “unconventional” circuits (at least to me) I often find myself unable to see whether components are truly in series or parallel, and how I should approach the problem. Mostly it is because of a weird location of a source (in a bridge, in one of the limbs of a delta/wye etc.). Consider the diagram below, where the open circuit voltage Vok should be determined.

Can someone help me with this? Not just the answer, but especially the reasoning behind the approach please.
Determining whether two components are in series or parallel (or both, or neither) is pretty straightforward. The following is for a circuit consisting of nothing but two-terminal devices.

Two components are in series if any current that flows in one MUST flow in the other.

Two components are in parallel if any voltage that appears across one MUST appear across the other.

Given a diagram, if two components are connected at a certain node and there are no other components connected to that node, then they are in series. If two components share the same node on both sides, they are in parallel.

To see the latter case, you can highlight each node in a different color, if a particular component is connected to the red node on one side and the blue node on the other, then it is in parallel with any component that is connected to the red node on one side and the blue node on the other.