Hey 2nd Year,
I hope you are all staying warm out there. Everyone seems to have varying opinions, but I personally would always choose to be too hot as opposed to too cold. It was all about layers.
I am writing to say hi and see if everyone is doing okay on homework. As for me, I am doing ok on mine. Capacitance jumped me a little but I have since beat it back a bit. Just remember it adds the opposite of Resistance. Also, watch out for what has positive angles versus negative ones in regards to Reactances. In series, inductive reactance is 90 degrees positive and capacitive reactance is 90 degrees negative. (They are 180 from each other.) In parallel, the inductive reactance is 90 degrees negative and the capacitive reactance is 90 degrees positive. Values calculated for resistors are always in phase at zero degrees.
One of the real keys to understanding AC theory is understanding how to find Z. In series, impedance triangles are your bestest friend. In parallel however, one cannot…NOT….not…N O T. (I have tried it ..ugh)..not make impedance triangles. Therefore, in order to find Z in a parallel branch, one must calculate the current through each component and make Current Triangles. The current through a resistor is at 0 degrees, the current through a capacitor is at 90 degrees, and the current through an inductor is at -90 degrees. Once you find the Current total (using Pythagorean), good old Georg Ohm comes in to play. Z equals the voltage divided by the current.
As I said, the key is knowing how to compute Z. In series use impedance triangles. In parallel use current triangles.
Hope that helps. If not, I am very sorry….and no, you cannot get back those 2 minutes of your life. maniacal laugh!!!
Greg Greiner
LU112 NECA JATC
Instructor
No comments:
Post a Comment