Electromagnetics question

[Qacer]

My friend recently received his PhD, and I was reviewing the solutions to some Electromagnetics problems on his website: website here

I am specifically curious about Chapter 1, Problem 1.8b. On his website, he stated that "The solution provided to problem 1.8(b) below is not completely correct. The right answer uses phi-sub-zero as 0, not pi/50.".

Can someone tell me where I went wrong?

I haven't dealt with Electromagnetics in a few years, so I'm kind of rusty. I am ashamed to say this because I was the TA for the class responsible for creating all those solutions. All those solutions that you see on his page took me at least 4 hours for each chapter. That is mostly due to writing out my thought process and color coding the text.

 

[esun]

One mistake I see is on page 7 of that document, where you write 7.5cm = 0.078m. Fixing that does not result in phi_0 = 0, though.

 

[Biftheunderstudy]

Ah but indeed it does, since then you get pi/2-0.5pi=phi_0 which is pi(1/2-1/2)=phi_0.

 

[Qacer]

Aha, thanks! No matter what I did to try and make it correct, I always make that kind of silly mistake. A few years back I took an Electromagnetics exam. For some reason, I wrote down 10*3 = 13 instead of 30. Luckily, the professor gave me the majority of the points because my steps were right.

 

[Biftheunderstudy]

I hear you, in a 4rth year Nuclear Physics final I added 8/2 + 3/2 to get 11 as the final step of a question. Unfortunately, my marker was much more anal and marked the question 1/9.

 

[BrownTown]

LOL, yeah I think we all have had those stupid little things where you mess up something completely trivial and then it is all on how big of a d*ck the grader is. The real bad one can be writing computer programs, I remember one where we made a raytracer (the final project for the class) and the inputs were supposed to assume the viewing window went from (0,0) to (800,600) and I did what we had always done in class with (-1,-1) to (1,1) and therefore nothing at all displayed and I got a 0. fortunately I was able to bargain with the techer and prove it really did work, but I still only got a 60/100 for something I should gotten ~95 on (teacher said he had to give me an F for it not working, so more or less lost 30 points for that little mistake 🙁).

 

[TecHNooB]

Originally posted by: BrownTown
LOL, yeah I think we all have had those stupid little things where you mess up something completely trivial and then it is all on how big of a d*ck the grader is. The real bad one can be writing computer programs, I remember one where we made a raytracer (the final project for the class) and the inputs were supposed to assume the viewing window went from (0,0) to (800,600) and I did what we had always done in class with (-1,-1) to (1,1) and therefore nothing at all displayed and I got a 0. fortunately I was able to bargain with the techer and prove it really did work, but I still only got a 60/100 for something I should gotten ~95 on (teacher said he had to give me an F for it not working, so more or less lost 30 points for that little mistake 🙁).

OUCH.

My sympathies.