Marks to Date

Please verify your marks.

Bring any errors to my attention please.

Note that I scaled the midterm marks.

Review Questions

Folks,

Here are some questions to try.

• Sample Questions
• Last year's final

We'll talk about them tomorrow.

QUESTIONS AND ANSWERS

Please use this blog entry to post questions in the comments section. Please feel free to answer any posted questions that you can.

Many hands make light work.

Confirmation

Just to confirm:

We'll have an exam review and problem solving session tomorrow afternoon, from 4pm until 5:30pm, in room 208TB (same room).

If you just can't make it, don't fret. Mark Wyville will repeat the exact same information on Monday morning at the usual class.

I just felt it was important that I see you personally before your exam. Without getting all gushy, I do want you all to do as well as you can.

See you tomorrow!

----------------
Additional info added Friday evening:

Just so there is no confusion:

It's a review.

It will be repeated on Monday December 1st.

It is not a repeat of a previous class.

Emergency Class

Folks,

I have just received a court order to appear in Federal Court at 9:30am, 30 McGill Street, Montreal, on Monday December 1st.

The judge gave me no other option. If I don't appear, I will be in legal trouble.

However, personally and professionally I cannot bear to not give you my last lecture for the course.

Consequently, I am going to arrange a lecture for Saturday, late afternoon.

For those who cannot make that lecture, one of the TAs will repeat it during the usual time on Monday.

Please indicate via a comment left on this blog whether you will attend the Saturday lecture. Also, please pass the word around to your classmates.

The lecture will review the course material. I will indicate what is on the exam. I will do some sample problems for the exam.

Hope to see you all on Saturday.

I will post the exact room and time as soon as I get it arranged. Check back here tomorrow evening.

By the way, I will be in my office tomorrow afternoon for those who need to discuss their midterm marks. I have decided to scale the marks, and will post those as well, probably tomorrow after I see how the make-up midterm went.

Canceled Lab

Sorry about that canceled lab. The TA apologizes profusely.

Can everyone who missed out on the lab on Monday show up on Monday, Dec 1st to do the lab? Of course, feel free to join any of the lab sessions this week if you are able.

If you aren't able to attend Monday, and can't make a session this week, send me an email with the subject "3105 Lab #5 make-up date and time?"

Midterm Bonus Marks

A number of people tackled the "bonus" question for the midterm. Some of the answers were "textbook quality". With the permission of the authors, I will post those answers.

I marked the bonus questions. This was an extremely difficult problem, so if you did well on it, you earned 3 or more out of 5. One person got the 7/5.

Here are the marks by student number:

100274446 5
100305696 3
100328362 3
100653270 2
100667964 2
100683668 2
100689100 1
100698479 2
100707035 5
100707894 5
100709295 5
100712016 7
100712985 5
100713959 1
100715209 5
100715251 5
100718154 0
100721347 0
100723938 3
100724629 2
100737212 1
100746202 1
100746668 5

Make up midterm

Folks,

This is confirmation that the make-up midterm will be held Thursday, November 27th, at 5:00pm until 6:30pm, in room 334AP.

Igor Miletic will proctor the exam. His phone extension is 8357 should you require to contact him.

The make-up midterm will cover the same material as the midterm did.

Midterm Marks

Wowsers, those midterms marks were low. I had to ask the TAs to double check. The average was only 10.3 out of 25. That's before the bonus question is added on (more on that in a post later tonight).

I first thought, ok, maybe the test was just too long. But then I looked through the midterms, and truthfully the questions that were done were poorly done. Too many mistakes, and too many people just didn't know what they were doing.

The problem I see is simple: lack of practice solving problems. We need to address this and pronto. Tomorrow the course material will be completed.

By this weekend, I will post a bunch of magnetostatics problems on this blog. Make it your #1 priority to work on them over the weekend. Monday morning we will go through them, and I will make myself available all day Wednesday and all day Thursday to work through problems with you.

For the record, here are some comments from the TAs on the marking:

Q1. Many students did not answer it and very few got almost perfect. Most students were in between.

For a) I gave marks for certain steps, such as setting up an equation for electric field, the integral, and so on. The average was probably something like 5/10.
For b) I usually gave 3 the marks if they tried "something", 7 marks if they had the correct method but their solution from a) was incorrect and thus their solution was incorrect (and they didn't note what it should be), and 10 if I could see they understood even if maybe their solution form a) was incorrect.

Here are my comments for Q2:

(a) A large majority of students got this question correct and received full marks.
(b) Most students attempted this question and got part marks.
-Marks were awarded for identifying the need to use the method of images.
-Marks were awarded for using correct equations and process.
-50% of the marks were awarded if the student failed to account for the image charge but nonetheless performed the calculations correctly.
-Minimal marks were deducted for small errors such as wrong signs and integration limits.
(c) Few students attempted this question.
-Marks were awarded for using correct equations.
-The remainder of the marks were awarded in proportion to how well the differential calculation was performed.
(d) As instructed, each student received full marks for this problem due to the typo in the question.

Comments regarding Q3 in the midterms:

1. For b), most of the students do not realize “r” is a vector, they use r=(a^2+z^2)^0.5 directly.
2. And some students use the wrong formula, such as the one for potential.
3. For b), some students misunderstand the question, they got E only for the z-direction not the E filed along z-axis.
4. For c), most students use the right formula, however I don’t know why they did not find out the total charge is zero.
   

The way I made the marking:

1. For a), as long as they drew a circle representing the charge loop, indicated z-axis, alpha, theta, I gave full mark – all the students did well.
2. For b), correct simple formula – I give 2; Express r as a vector in terms of x, y z – I give 5; some steps wrong in the middle – I give 8; final answer wrong – I give 9;
3. For c), as long as the formula is correct – I give 5; because the calculation is simple, if something wrong in the middle (like wrong explanation on why the total flux is zero) I give 5.

For the first part of question 4 (figure sketch), at the very least they had to identify the axis, the location of the charge density (plb and pla), and the location of -ve and +ve alpha and beta. Most people gave a complete figure sketch.

The second part of question 4 was partitioned up as follows:

Getting Coulomb's Law right was 2/10.

Equating q1, q2 to the product of the charge densities (pla and plb) and the radius, r; and r in terms of the variable distance along the charge distribution (r = x1 - x2 for example) and then substituting back into Coulomb's equation was 3/10.

Setting up the integral properly and recognising that a double integral would be needed was 4/10.

Solving the integral was 1/10.

Common errors including not setting up the radius properly and not using a double integral.

Missed the Midterm?

If you missed the midterm, please contact me!

I'd like to have the make-up midterm this coming week.

I'm thinking some evening would be good.

Maybe Thursday evening?

So, if you missed the midterm, let me know if you can make it on Thursday evening.

Last Lab!

Hi Folks,

I'm sure you have all been waiting to hear that we are about to start your *last* laboratory of the course.

The material concerns magnetostatics, and you'll be simulating solenoids. By now, you should understand a bit about the magnetic field within the solenoid, based on the lectures. This lab lets you explore the magnetic field using the computer model.

You can find the laboratory write up HERE.

Midterm Marking Comments

This is what I just send to the TAs:

Folks,

The solutions to the midterm are here.

Please become an "expert" on your own problem. There will be a variety of solutions for each problem, so mark accordingly. Students who set up the problem correctly but didn't finish the integrals required to give a final answer should still receive a good mark. Give these students roughly 50-70% of the points for setting up the problem well, and demonstrating that they could have completed the problem eventually. Just make sure you mark consistently. Please give an explanation each time you deduct points. If that becomes repetitive, make a sheet containing the frequent mistakes and corresponding point deduction. I will post this at a later date.

Let's get this marked and returned to the students by next Monday.

Please let me know if you find any errors in the solutions.

Midterm Comments

I met with the TAs today to discuss marking of the midterms. We plan on having them back to you on November 24th.

The TAs mentioned that there were lots of complaints that the midterm was too long.

The midterm was not too long if you practiced the problems given beforehand. If you didn't do so, then for sure you would not be able to complete the midterm.

I looked through the midterms, and some people did well. Others could not even start some problems. It is the latter group that concerns me. Even if you could not complete every problem, you should be able to start them.

I asked the class how many problems would be fair, and five or six problems was considered as fair. I offered less (two), but then the danger is not being able to complete either.

Let's wait and see how the mark distribution turns out before I comment further.

For the record, the questions will be marked as follows:

Q1 -- Barbora
Q2 -- Greg
Q3 -- Zhan
Q4 -- Chris
Q5 -- Lidija
Q6 -- Ming
Bonus Question -- Len

My answers to the questions and marking instructions to the TAs will be posted here later tonight.

PA Problems for Next Week

Hi Folks,

This week let's try something a little different.

You can find your PA session problems for next week HERE, along with the solutions. Please review the problems *and* the solutions before attending your session.

More on Bonus Question for Midterm

Note: you can bring your solution with you to the midterm. Please sign it, and hand it in before the midterm starts.

Motors Lab

The fourth laboratory concerns motors. A copy of the lab is HERE.

Yes, I know we haven't covered motors yet. Such is life in 3105. However, we will cover it soon, and you should recall what you do in the lab when I am talking about motors in the classroom.

Office Hours The Week of November 3rd

This Friday I will be away.

I'll be available for consultation this afternoon, between 1pm and 3pm, in room 334AP. If I'm not there, try adjacent rooms.

I'll also answer emails concerning the course up until Saturday evening.

The TAs are also available as usual and will be happy to help you prepare for your midterm.

Practice Midterm Blues

Well, I'm sitting here proctoring the "practice midterm", and there are only nine students writing it. That's 10% of the class.

I think my lesson here is that I won't do this exercise again. I hoped that people would seriously try to solve it, and then I would be available afterward to discuss the problems.

However, hopefully all the practice problems will help many of you to do well on the midterm next week.

I'm not posting solutions for the practice midterm, because the questions are so similar to those solved in class (or by Ming in the PA sessions this week).

Also, I'm not planning on posting the sample midterm. If you have a valid reason for not showing up today to get a copy, send me an email and I'll "see what I can do".

Bonus Question for Midterm

Folks,

Just a reminder:

If you can solve the following problem and bring your solution to the midterm, it is worth up to 5 points added to the rest of your score (maximum score is 100% though).

The problem:

You have a circular loop of current in the xy-plane. The loop radius is "R". The current in the loop is "I" and flows counter-clockwise when viewed from the positive z-axis. Find the magnetic field vector "B" for any point in space above the ring.

The absolute best correct solution will receive 7 points. If no solution stands out, then no one gets the 7 point bonus.

PA Problems for the week of November 3rd

I hope everyone had a fright-filled Halloween.

I'm still on a sugar high due to candy confiscation and sampling.

Please find your PA questions for the week of November 3rd right HERE.