I Why wouldn't two inductors provide a lag of 180 degrees?

[PLAGUE]

TL;DR Summary

I know, people come up with answers such as, if it were the case that two inductors make current lag by 180 degrees, then it would be possible that you cut down a big inductor, which would make a lag of 90 degrees, and make a current lag of 180 degrees with the smaller inductors. Yeah I understand that is the logical answer but I wanna know what in fact happens in the inductors!

This says,

When you apply a voltage to an inductor, you make a magnetic field. Henceforth, if the magnetic field varies with respect to time, there is an electric field that opposes the magnetic field inside the inductor. In other words, the electric field generated by the voltage behaves like a wall to the magnetic field generated by the current.

If so, then why wouldn't two inductors provide two walls and make the current lag by 180 degrees? I know, people come up with answers such as, if it were the case that two inductors make current lag by 180 degrees, then it would be possible that you cut down a big inductor, which would make a lag of 90 degrees, and make a current lag of 180 degrees with the smaller inductors. Yeah I understand that is the logical answer but I wanna know what in fact happens in the inductors!

 

[tech99]

An inductor is analogous to a heavy mass. Once it is moving it requires a force to slow it down. It has inertia. If I divide the mass into two, each will now require only half the force to slow it down, but the timing of the new forces remains the same.
In a similar way, if I have two inductors that are in series and carrying a sinusoidal current, each will have a voltage across its terminals which leads the current by 90 degrees, and the two voltages will be in phase. So they will add up to the total for the two inductors, and each will still be leading the current by 90 degrees.

 

[DaveE]

I'll assume you know a bit of calculus. If not, no worries, you can ignore this for now.

For inductors the relationship between current and voltage is $v(t)=L \frac{di(t)}{dt}$

For a single loop circuit with a voltage source and two inductors:
$v(t)=L_1\frac{di(t)}{dt} + L_2\frac{di(t)}{dt} = (L_1+L_2) \frac{di(t)}{dt}$

Since the inductors have to share the same current you can just add them together. Just like adding capacitors together in parallel because they have the same voltage.

 

[Baluncore]

If so, then why wouldn't two inductors provide two walls and make the current lag by 180 degrees?

Because in any one inductor, it is the current in that inductor that lags the voltage across that inductor by 90°. Fundamentally; v = L⋅di/dt .

To get a lag of 180°, you would need (a resistor) to convert the current in the first inductor, into a voltage, to apply to the second inductor, so you could measure the phase of the current in the second inductor, relative to the voltage applied to the first inductor.

Without the resistor, there will be no conversion from current to voltage at the junction, so no opportunity to get another 90° of lag.

With the resistor, you no longer have two simple series inductors, you have a 'T' connected LRL network.

 

[PLAGUE]

Because in any one inductor, it is the current in that inductor that lags the voltage across that inductor by 90°. Fundamentally; v = L⋅di/dt .

To get a lag of 180°, you would need (a resistor) to convert the current in the first inductor, into a voltage, to apply to the second inductor, so you could measure the phase of the current in the second inductor, relative to the voltage applied to the first inductor.

Without the resistor, there will be no conversion from current to voltage at the junction, so no opportunity to get another 90° of lag.

With the resistor, you no longer have two simple series inductors, you have a 'T' connected LRL network.

You mean something like this?

 

[Baluncore]

You mean something like this?

Yes, exactly.
It requires a more complex network, not simply two inductors in series.

 

[Gavran]

An inductor is a reactive electrical component that stores energy in a magnetic field. It does not dissipate energy and a current lag is 90 degrees.
Two or more inductors means two or more magnetic field energy stores and there is not a dissipation of energy. Again, there is a current lag of 90 degrees.

 

[sophiecentaur]

Yes, exactly.
It requires a more complex network, not simply two inductors in series.

A chain with inductors and capacitors constitutes a delay line which can introduce any phase shift you require with enough stages.