# Transition from mechanics to electricity and magnetism.

1. Jan 18, 2009

### Eric_meyers

Ok, I finished my physics I calculus based class, and really I don't feel like I learned a lot or mastered the material. I would spend many minutes nearing hours trying to think over my homework but with a load of other classes and the fact that we got all the hard and I do mean hard problems (some 55 problems per week) in which some even the professor himself got stumped on, I really couldn't make much progress and neither could my peers. I ended up with a B+ but again, I rate my experience and knowledge with physics at an F.

Now I'm going into physics II. I'm going to make a commitment to working in this physics class everyday, but I want to know what kind of class this is. In your opinion are the concepts and problems harder than mechanics and what kind of questions can I expect? I assume with electricity and magnetism the problems will be focused on more of concepts rather than abstract geometry like mechanics was. I consider myself fairly strong in solving conceptual problems, but geometrical problems I lack even fundamental logic. For instance figuring out a root equation to the change of position in a pendulum involved 1 - cos (theta) I still don't understand, or why oscillating motion moves in A sin (bt - phi) manner... or any of that.

Well anyways I digress, I'd like to hear your opinions on what to expect in electricity and magnetism.

2. Jan 18, 2009

### symbolipoint

The meaning of what you said in paragraph 1 is understandable. You feel that way maybe because of having less conditioning and experience with mathematical problem solving. The effect of Physics 1, although the course is difficult, should be to develop analytical problem solving skills incorporating algebra and drawing of figures.

Your Physics 2 (Electricity & Magnetism) differs because there are more features with periodicity, and because there are positive and negative charges; gravity does not have this kind of character. (Gravity is not characterised by anything like opposite charges - at least not at this level of study..., ?). This E&M course is much, much more difficult than the mechanics Physics 1 course. You will need skill in using Algebra at the intermediate level, strong Trigonometry skill and understanding, and much intensive use of Calculus, including strong familiarity with Analytical Geometry.

3. Jan 18, 2009

### Eric_meyers

Well.. I'm screwed. Luckily I have an electrical engineer for a dad who can help me with this stuff.

4. Jan 19, 2009

### descendency

As long as you understand newton's basic laws, stuff about waves (especially towards the end when you talk about EM Waves), superposition, etc. you'll do fine.

The vast majority of EM physics is self contained. You'll learn 5 basic laws (Lorent'z force law, and the 4 maxwell equations which can derive quite a few simple shortcuts) and how to derive the important information from them.

It's less important to have learned the material per se (you won't see a great deal of material on static friction for example) and more important to understand the process you go through to find answers.

5. Jan 19, 2009

### Eric_meyers

^mmm can't say that I do. I don't recall going over EM waves at the end of my mechanics course but maybe because we simply got behind or it's not intended to be in the syllabus - I'm not sure.

One thing I do know is that if I work hard enough everyday then I'm doing my part.

6. Jan 19, 2009

### descendency

Generally you cover waves (the rope diagrams - where end of the rope is flipped and the wave is followed to the other side).

EM waves are the end of the EM section.

7. Jan 19, 2009

### physics girl phd

Depending on what kind of Calculus sequence you have (a two semester or a three semester course) you may or may not cover EM waves in Physics II (or even mechanical waves in Physics I)... if your sequence has a third semester, often mechanical waves (including waves on a string and sound) and E&M waves will be one of the first topics in the third sesmter course. (As a common subtitle to Physics III -- Waves, Optics and Modern Physics -- might suggest). So i would worry less about that part of the curriculum (check your student handbook for the course description).

What I would worry about is having a strong calculus background. Many of the first problems in EM involve integrating over the volume (or area) of a charge distribution... to find things like force, field, and potential. Often in these problems you have to be smart... force and field are vectors so you need to be careful about the function(s) you integrate. You also have to be smart about symmetry. Later you may need to integrate over area to find fluxes (which relate to the net field passing through a given area). A good understanding of gradient is also useful. I really suggest that you have strong mastery of Calculus II (usually basic integration methods) and Calculus III (usually dominated by vector calculus). Unfortunately, the introductory Calc physics sequences tend to require a corequisite of Calc II, when they should really require a corequisite of Calc III. I think many students' performance in EM isn't what it should be because of poor mathematics preparation.

Also note, your dad may be helpful (if he liked field theory classes and retained that knowledge). Typically the EE sequences I see contain only 1-2 courses in this type of material (it can depend, some electives out there in optics could be quite helpful, especially wave guides, but I'm not sure how common those courses were in his day). Otherwise, much of the electrical engineering coursework tends to focus on circuits, digital and analog signal processing, etc. Many EE's I see out there still hate the EM physics treatment because of the emphasis on fields (only a small part of the course (maybe up to 1/3) deals with circuits (which he should be able to help with -- EE's typically have far more extensive electronics courses than physics majors).

Good luck! It's my favorite subject matter personally... but my least favorite to teach because students struggle so much with it!

8. Jan 19, 2009

### Nick M

Yeah, I'm definitely of the opinion that people should have Calculus II finished for Physics I, and Calculus III (Multivariate) as a pre-requisite for Physics II.

I got an A in Physics II - but I understood very little of it. After finishing Calculus III last semester, I've been spending the winter break re-reading my Physics II sections along with the book, "Div, Grad, Curl, And All That".

I really think 4 years for an engineering degree is too quick. Think about what you can do by adding an extra year. First year take Calculus I/II, Chemistry I/II, Intro Engineering courses, and Social/Humanity electives. Second year treat as your "Freshmen" year taking Calculus III, Diff-EQ, Linear Algebra, Physics I/II, Orgo I/II, and remainder of Social/Humanity electives. Then you have three solid years of engineering courses - with room for 8-10 additional higher-level courses having done your Social/Humanity requirements in the beginning. I've adapted my schedule to fit this style.

But anyways - keep at it and realize you might not understand everything that you're doing.

9. Jan 19, 2009

### Eric_meyers

Thanks for your very elaborate and intricate reply! Yes we do have a 3 sequence physics and 3 sequence calculus course. I earned an A in integral calculus or calculus 2 and I'm taking calculus 3 which is vector calculus this semester. Calculus itself doesn't really seem to bother me it's geometry - geometry of vectors which I have trouble with. I never really had a solid geometry background and free body diagrams etc had to be memorized instead of mastered for my survival in mechanics class.

I need to get a hold of something to remedy my discrepancy in geometry that much I do know.

I heard Calculus 3 is often easier than Calculus 2, but I found integrals fairly easy and infinite series extremely easy. Anyways, our physics 3 is indeed wave, optics, and modern physics. (Do you teach at UT Austin?)

Well anyways about the integrals involved in physics II, I'm guessing I'll be given problems where I'll need to relate variables into a standard equation and then integrate that function?
Sort of similar to finding the center of mass of an irregular shape? I.E. we had a problem involving a bucket and water and we had to go to our professor to learn how to get the center of mass of that thing involving many intricate vectors etc. etc.