Does placing two inductors in series make a current lag of 180 degrees?

AI Thread Summary
Inductors cause current to lag voltage by 90 degrees, and connecting two inductors in series does not change this fundamental behavior; the current still lags by 90 degrees. The discussion highlights that while inductors sum to create an equivalent inductance, the phase lag remains constant. The analysis of circuits often focuses on voltage phase shifts between nodes, which can vary and are not always exactly 90 degrees. The conversation also touches on the importance of understanding impedance in complex circuits, particularly in transformer models where inductance is treated as reactance. Overall, the principles of inductance and phase relationships are crucial for effective circuit analysis and design.
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I understand that inductors make current lag voltage by 90 degrees. What if I connect two inductors in series? Would that make current lag by 180 degrees?
I understand that inductors make current lag voltage by 90 degrees. What if I connect two inductors in series? Would that make current lag by 180 degrees?
This question arose when I was studying the equivalent circuit of a transformer.
Screenshot 2025-04-25 185149.png


If Ip goes through Rc and Xm, does it mean that Xp would make Ip lag by 90 degrees and does that mean Xm would add 90 more degrees of lag in the current?
 
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Inductors in series sum, to make one inductor. That still only gives a current lag of 90°.
 
Interesting that having been involved with electricity and electronics since I was 8 years old or younger nowhere in my early years of self education did I wonder if that could be a thing. After a bit of book learning I guess I knew better than to question it. Believe me when I say I did have a great many misunderstandings early on. That's what happens when messing with electricity early in life. My parents likely worried I would burn the house down.
 
I think this question arose from the fundamental behaviour of inductance, v=L⋅di/dt, which for a sinewave, always has an exact 90° lag of current to voltage. The calculus of trigonometric functions decides that.

When we analyse circuits, we tend to look at and compare, the voltages on the different nodes, because we can measure voltage with a meter, or an oscilloscope, without breaking the circuit to insert an ammeter to measure the current.

We see varying phase shifts between the voltages on the nodes of the circuit, which are rarely exactly 90°. By changing the circuit components, we can use the circuit to build frequency dependent filters, or implement AC and DC coupling, that can make the circuits very useful for signal processing.

In complex circuits, it is voltage phase between nodes that we analyse. In those models, there are almost always, different R, L, or C, series and parallel components shown, that prevent a simple series or parallel combination of like components.

In the theoretical model transformer, presented by the OP, the virtual components have been separated as impedance components, Z=R+jX, as part of the analysis. Note that Np and Ns are the turn counts of the primary and secondary windings of the transformer, not inductors. The inductance of those windings is modelled separately, as reactances, jXp, and jXs.
 
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