Drawing Root Locus plots by hand is a hard and time consuming task so it is always good to check the answers with Matlab just to be sure you are on the right track.

The process of drawing the Root Locus with Matlab is as follow:

1. Define the numerator (num).
2. Define the denominator (den).
3. Draw the Root Locus (rlocus (num, den))

So let’s say we want to draw the root locus for the following system:

G(s) = k / ( s )*( s^2 + 4s + 8 )

The Matlab code will be:

1. num = [1];
2. den = conv ([1 0] , [1 4 8]);
3. rlocus (num, den)

I’m taking GMAT exam next week. GMAT is the exam needed for an MBA application. I have been studying quite a bit for it, but it is never enough.

GMAT score ranges from 200 to 800. The median score is 500. Most good MBA school want above 600. However, schools like Harvard, Yale, Columbia, Chicago and likewise like to see a score of 700+.

GMAT is three parts: English, essay, and Math. The Math part is easy as long as you don’t make stupid mistakes but the English and essay part can be challenging which in fact they are.

My plan is to finish the Kaplan GMAT book, and take at least 4 other sample tests before taking the GMAT. I will sign up for an exam date toward the end of October. The test costs $250 each time you take it. It would suck if I do poorly the first time and have to retake it.

I will post any GMAT and MBA tips that I learn along this path on my blog as well.

Question: On TI 89 Calculator how can I switch from Radians to Degrees?

1. Select “MODE“
2. Scroll down to the line that reads “Angle………………………..Radians”
3. Click “ENTER” and Change “Radians” to “Degrees”.

Here are some important points I learned in my readings of chapter 1 of Electromagnetic Motion Devices:

• In all electromechanical devices, mechanical motion must occur (surprise!!). This motion reflects into the system as a flux linkage (in electromagnetic systems) or charge change (in electrostatic systems).
• Amperes Law. (Ni) is the current enclosed in a close loop circuit and has the units of (amperes), however it is commonly referred to as Ampere-Turn (At) or Magnetomotive Force (mmf).
• Generally (from what I understand) the way to solve the work out problems in this section is to
  1. draw the equivalent electric circuit diagram of the magnetic system
  2. calculate different R values (reluctances of different paths on the system) and come up with equivalent reluctance of the whole system
  3. Put all the know and unknown information into the ? * (R1+R2) = Ni equation.

I have started studying ELectromechanical Motion Devices by Paul C. Krause and Oleg Wasynczuk. I will finish the book (hopefully) by end of summer. As I read through the chapters, I will write notes and solutions here.

This way I can be sure that I have learned the material and also if someone can find any mistakes in my understandings he/she can point it out by sending a comment.

If everything goes well, I should have a new post on this topic every other day.