Physics 4BL: An Undergraduate Laboratory Course in Electricity, Magnetism and Optics

Reiner Stenzel, UCLA, April 2007

Introduction

The objective of this course is to teach electricity and magnetism (E&M) by observations from experiments. This approach complements the classroom experience of Physics 1B,C where you learn the material from lectures and books designed to teach problem solving skills. Historically, E&M evolved from many observations that called for a theoretical explanation. It is a great achievement that all classical E&M phenomena can be explained by four equations, the so-called Maxwell's equations. This laboratory course is designed to perform experiments showing the validity of these equations.

The Physics 4BL room

In the laboratory, you will have different experiences than in the classroom. In the real world, there are no point sources, no infinities, all measurements have errors, and sometimes things don't work out as expected. A broken instrument or wire can be as frustrating and time consuming as trying to solve a seemingly impossible homework problem. You will have to learn patience and persistence to make good measurements.

For solving theoretical problems you first need to learn the appropriate mathematical tools. For performing experiments you first need to become familiar with measurement tools, called instruments. These include multimeters, oscilloscopes, signal generators, a Gaussmeter, digital scale, power supplies and computers. The first lab session is devoted to acquaint you with modern digital data acquisition methods. It is expected that you are already familiar with Personal Computers (PCs) and basic software such as spreadsheets. In the lab you will record your data to file, copy the files on memory sticks or CDs and evaluate the results at home or a computer lab.

The previous 4BL course, which was taught with little change for the last 20 years, was very simple and easy. The new 4B Lab is designed to be more advanced and challenging. You are exposed to a wide spectrum of experiments in electrostatics, dc and ac circuits, magnetism, waves and optics. The level of the class is at or above the average material of the lecture class. The average student is unlikely to finish all of the assignments within a 3-hr lab session. If you want to perform most of the experiments and thereby obtain a high grade you must be well prepared before starting the experiments. This means careful reading of the lab manual, looking at the component pictures, knowing how to read a circuit diagram and how to make proper connections to instruments. Last but not least, you have to know the underlying theory. If you cannot get it from the lecture class you should read it from the textbook. It is highly advisable to take the lecture class a quarter earlier. If you take it simultaneously you may find poor synchronization between theory and experiments because of different instructors and different scheduling priorities. Remember, this is the only laboratory course in electromagnetism in our Department. You have a great learning opportunity; if you miss it, you won't have another chance.

For each experiment you are supposed to write a laboratory report. It should contain a very brief description of your experiment (no need to copy the lab manual), the data obtained (usually in the form of graphs) and evaluations such as line, surface and volume integrals, curve fitting, circuit analysis, and any questions raised in the lab manual. The report should be written concisely in a scientific language; it is not an essay where you admire the beauty of science or express your frustrations with the equipment. The TA has no time to read excessively long lab reports. He/she will only look for correct answers and understanding of the results. The reports are due a week after the experiments have been done. Submit an electronic file of your lab report to Phys. 4BL, "TurnItIN". Data are shared within an experimental team but the reports should be written individually. Copying other reports constitutes plagiarism and will be reported to the Dean of Students with unpleasant consequences. Bring a personal notebook to the lab to keep a record of what you did. The TA will grade it as well as your lab performance. The TA will explain what he/she considers important for a high grade, which will include proper preparation prior to the lab as checked by quizzes, efficient work during the lab, good collaboration in your team, bringing up interesting questions, etc. The TA will help you if you have specific questions but he/she will not set up the experiments for you.

It is general policy to announce the grading method for each course. For large lower division courses, curve grading is common. It is essentially a ranking scheme, which does not necessarily measure your true knowledge with respect to some absolute standard. This can have unusual consequences: You may get a high grade for learning very little if the majority performs poorly. Vice versa, you may get a poor grade for doing a lot of work if you have a tough competition. Always try to be better than the average; that’s the rule in real life. In order to know where you stand, frequently compare your report grades with the section average and standard deviation that the TA will announce. Learn about normal distributions and understand the method of grade calculation described below. All this will help avoiding misunderstandings at the end of the quarter.

Finally, the course grade will be determined from three contributions with different weights:

Comments:

• Lab reports are graded by your TA on a scale of 1 to 10. High grades are obtained for correct results, good discussions, and a clean, concise format.
• Pre-lab Quizzes are written by the individual TA. They will test whether you have read the lab manual for the upcoming experiments and whether you understand it. If you come unprepared, you will not accomplish much.
• Lab Participation will be judged by your TA on a basis of attendance, preparation, participation and collaboration. You will lose points if you handle equipment without care and cause damage.

The Final Course Grade will be determined by "curve grading" which works as follows: Each TA will determine the mean and standard deviation of the percentage grades in his/her groups. The instructor assigns the following Letter grades:

• Mean value equals a B+ (or a numerical grade of 3.0)
• One standard deviation corresponds to a change by one letter grade. For example, one standard deviation above the mean equals an A+ (or 4.0).
• One standard deviation below the mean equals a C+, two standard deviations below the mean is a D+, etc.

More precisely, the numerical grade y is calculated as follows:

where x is the weighted total grade, m the mean value and sigma the standard deviation within your section.

Letter grades with plus and minus values are assigned from the numerical grade as follows: