Series-Parallel AC Circuit Analysis (Full Lecture)

In this lesson we'll examine series-parallel AC circuit analysis techniques by way of a collection of illustrated example problems. (Full Lecture)

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[bigbadtech]

Voltage divider ruler formula at 31:47 should read V1=Z1/(Z1+Z'')E (ie: NOT Z')
V3 at 33:41 should be 5.8V at an angle of 0.1 degrees (ie: .054 degrees)

[spelunkerd]

I have to chuckle, since your advice to avoid taking apart the whole car to find a quarter under the seat was exactly the unnecessary work flow I use. It made me wonder why I do that. Of course we're only talking about a task that does not require the intermediate info. Those divider rules allow one to skip calculating the total current for a pure series circuit or voltage drop across a pure parallel circuit, but if you need those answers anyway you aren't saving as much work. The painstaking task of all these calculations is phasor addition and subtraction, which is required in any case since both divider rules use total impedance for the denominator. I guess what draws me back to getting intermediate info, is the grounding, intuitive feel for exactly what these calculations mean. Once I get total current in a series circuit, the rest is just ohm's law, there is no need to memorize secondary formulas. Likewise, once I get that intermediate step of voltage drop across a parallel circuit, it's all back to repetitive easy work with ohm's law, no need to remember extra formulas. If I make an error along the way, it is easier to quickly identify where the error is, fix it and move on.

[andrewholden]

Awesome lesson, Jim I came to a stunning conclusion messing around with my calculator the other day. I have been pondering on the equation Ic = C(dV/dT) lately and discovered something beautiful I thought you may appreciate.
As your lesson states, voltage on the plate of a capacitor lags the current flowing to it by 90°.
I was curious about these equations and wondered if they were compatible, so I decided to take the derivative of a sine wave. What I found blew my mind and caused me to look at AC analysis from a different perspective. The reason reactive components put voltage and current out of phase by 90°, appears to be due to the fact that the rate of change is highest at the zero crossings in a sine wave, and the rate of change goes lower and becomes 0 at the peaks.Thus, The derivative of a sine wave yields another sine wave that is shifted 90°.

An example: Ic = 120V / (1 ÷ (2π(60)(10μF)) = .452389 @ 90°
But also:
Ic = 10μF(dV/dT(120sin(2π(60)(T)) yields .452389 at T= 0 since current is shifted 90°. This allows you to find the current flowing through the capacitor at any given time. Math is so beautiful when you can find these connections!!!

[roseelectronics]

Great tutorial! Hope to see lectures on semiconductors.

[Jnglfvr]

At 34:08 the first formula on the upper right should read: V1 = Z1*E/(Z1 + Z''). Since you got the answer right (39.8<4.2) I assume that Z' was a typo. As written with Z' that would have made V1 = 34.8<12.2 which is incorrect.

[djtfan]

V_3's phase is wrong, it should be 0.1 to 0.8, according to your formula, and my calculations.