Introduction:

These lab instructions are probably different than those you are used to. You will not find a detailed discussion of the principles explored by the lab; you will not find any algebra deriving the equation to be used in the lab; and you will not find step-by-step instructions telling the students what to do. These labs allow students to practice making decisions based on the physics presented in the other parts of the class: the discussion sections, the lecture, and the text.

The lab instructions are divided into 4 two to three-week units (labs), an equipment appendix, and five technique appendices. The labs themselves are comprised of an introduction page and several problems. Notice that we do not do experiments in our laboratory. Rather, we do problems which are similar to the ones found at the end of a textbook chapter or on a quiz, for the students to solve and then compare the solution to nature. Typically an problem should take the students about an hour to complete (if they have done their homework). They should analyze all the data and reach a conclusion in class before starting a new problem. The problems are further broken down into sections which represent the process expert researchers use in a laboratory. The sections are: introduction to the problem, description of the equipment, a prediction of the outcome, warm-up questions, exploration, measurement, analysis and conclusion.

Each problem begins by briefly stating the question which is the point of doing the problem. The equipment is then described in enough detail to allow the students to predict the outcome of the problem. The questions in the next two sections (Prediction and Warm-Up Questions) are to be answered by the students before they come into lab and will be handed in to the teaching assistant's mailbox a day or two before lab. The Prediction is the solution to the problem set forth in the problem. The Warm-Up Questions are designed to help the student either complete the prediction or plan the analysis the data before they come to lab. Typically the introduction to each lab class will begin when the you ask each group to arrive at a consensus about one or more of these questions and then put its answer on the blackboard. Then have a class discussion comparing and contrasting these answers. Remember, the purpose of the introduction is to get students to make an intellectual commitment to the lab. They do not need to arrive at the correct answer to the questions until after they have completed the problem. The exploration section encourages the students to get familiar with the apparatus so they will understand the range over which valid measurements can be made. The measurement section asks the students to think about the kinds of measurements needed to test the prediction. The analysis section asks the students to process their data so that they can interpret their results in the conclusions section.

Grading:

The grading system for lab is decided by a teaching team for a course (lecturer + teaching assistants). Students are typically graded on a 10 point scale, but this can vary across different teams to as many as 20 points. Students typically receive 1-2 points per week for their prediction and the answers to the warm-up questions and another point each week for keeping a competent lab journal. Each student is also required to write a lab report for one problem, which could be a different assignment for each member of a group. That problem is assigned by the instructor (teaching assistant) at the end of a lab topic, about every two to three weeks. This report should be a concise and self contained technical report which is essentially a clarification of the student's lab journal. It should only be about three pages in length.

To encourage cooperation in lab groups, the students should be awarded bonus points if everyone in their group receives more than 80% on the report (or a different percent as decided by team policy). You may want to generate a little peer pressure for preparation by giving bonus point if everyone in a group comes to lab with a complete set of answers for the prediction and warm-up questions.

 *  An "R" in the Points column means to rewrite that section only and return it to your lab instructor within two days of the return of the report to you.

 

 

Frequently Asked Questions:

What goals are addressed by these labs?

There are many possible reasons of doing a physics laboratory. For example, a lab could allow students to:

* confront their preconceptions of how the world works;

* practice their problem solving skills;

* learn how to use equipment;

* learn how to design an experiment;

* observe an event which does not have an easy explanation to realize new knowledge is needed;

* gain an appreciation of the difficulty and joy of doing and interpreting an experiment;

* experience what real scientists do; and

* have fun by doing something more active than sitting and listening.

It is impossible to satisfy all of these goals with a single laboratory design. Because this course follows the traditional structure of learning physics through solving problems, we have focused the laboratories toward PROBLEM SOLVING. Since the most important reason that our students cannot solve physics problems is that they have misconceptions about the physics, our second goal is to confront some of those misconceptions in the laboratory.

Why this style of lab?

Most physicists feel that labs are an essential part of a physics course because physics is reality. Some have gone so far as to state that all physics instruction should take place in the laboratory. Nevertheless, labs are the most expensive way to teach physics. Research to determine the benefit of labs in teaching physics has consistently shown that labs which give students explicit instructions in a "cookbook" style have little value, particularly to address a problem-solving goal. The research also shows that "hands-on" experience is an efficient way of overcoming misconceptions. In our teaching environment, the laboratory is the only opportunity for you to interact with small groups of students during an extended period. Because the students have specific and visible goals, it is easier for the instructor (you) to determine their physics difficulties by observing them. Solving a problem in the laboratory requires the student to make a chain of decisions based on their physics knowledge. Wrong decisions based on wrong physics lead to experimental problems that you can observe and correct.

How can I make my students like and value the labs?

Instructor attitude is the most important factor in determining what the students like. If the instructor likes the labs and thinks they are valuable, then the students will tend to like the labs. The converse is also true. Even before starting the class, many students consider labs as "busy work" which have nothing to do with the content of the course. Labs have required attendance, so some students see their object as getting a task done as fast as possible so they can leave -- the "take-the-data-and-run" approach. This view is reinforced when (a) students are given step-by-step instructions focused on doing the task as efficiently as possible; (b) the lab instructor spends a majority of the lab time helping groups get their apparatus working so they can get done; (c) the lab instructions have all necessary information so that no use of the textbook or the lectures is needed; and (d) the problems are not seen as challenging; and (e) there is no reference to the labs in the lectures or on tests.

The physical appearance of the lab is also very important in determining student attitude. Students will also dislike the labs if they are overly frustrated in their attempts to operate in the laboratory environment. An instructor who takes time to assure that the lab is neat and orderly before the students enter gives the message that the student's lab work is important.

Why have students work in groups?

The simplest answer is that a well functioning group is the most efficient way to solve any problem. However, in this class we have more definite educational reasons. Students working in groups must discuss what their thoughts are -- they get practice in "talking physics." This discussion tends to bring their physics preconceptions (alternative conceptions) to the surface so they can deal with them. It is a cliché that the "best way to learn is to teach" but it is true. Working in the same groups in both laboratory and discussion section allows students to become more familiar with each other so that they feel comfortable enough to discuss their physics difficulties. Having the same groups and instructor for both the laboratory and discussion section also explicitly connects the lab to the rest of the course. In addition, students working in groups make teaching more manageable for the instructor. Instead of trying to serve 18 individual students, you interact with 5 or 6 groups, so you can be their "coach" to help them become better problem solvers. By pooling their knowledge and experiences, members of a group will get "stuck" less often which leaves the instructor freer to concentrate on groups which are on the wrong track.

Why are there so many problems in each lab?

These labs have been written so that there are more problems than the typical group can complete in the time allotted. This emphasizes that the function of the lab is to learn the physics not to get the problems "done." The course teaching teams for each course can then choose a preferred order of problems and the minimum number of problems to be completed to match the emphasis of the lectures. In addition, the extra problems allow each lab instructor the flexibility to select the material to meet the needs of each particular group. Some of your groups may understand the material and need to be challenged with a more difficult problems to deepen their knowledge. This also keeps them from getting bored. Some groups will have difficulty in understanding the basic physics being presented and may need to concentrate on a single straight-forward problem or do a second very similar problem.

Why don't the lab instructions give the necessary theory?

This is to emphasize that the laboratory is an integral part of the entire course. The theory is available in the textbook and the preparation section for each laboratory gives which sections are to be read. Reading the text and doing the predictions and questions preceding each problem gives an adequate preparation for the lab. A computer check out is used to assure that each student has a basic understanding of the necessary text material before coming to class. Doing the lab problems should help, with the guidance of the lab instructor, clarify and solidify the ideas in the text and in the lecture.

What is the reason for giving minimal laboratory instructions?

One of the primary goals of the laboratory is to help students learn to solve physics problems better. Good problem solving requires informed decision making. Most of these students need a great deal of practice in making analytical decisions. The labs are designed to leave most of the decisions up to the students. As with any problem, usually there are several correct paths. Discussing the possible choices within the group gives each student the opportunity to solidify correct concepts and dispel alternative conceptions. This freedom also allows groups to make incorrect choices. It is another true cliché "that we learn from our mistakes". Observing these incorrect decisions allows the instructor to teach to the needs of the particular students or groups.

Why should the students write up lab problems?

No matter how conscientious the lab instructor is, many students will leave the lab with some of the same misconceptions as when they entered. The presentation of the course material may also generate new misconceptions. Reading a student's words gives the instructor valuable knowledge about that student's knowledge of the physics. This can help you direct your teaching more effectively. In addition, these students need to begin the process of clear, concise, meaningful written technical communication that they will need in their careers.

What is the function of the pre-lab computer check out?

These questions are designed to make sure that students have read the relevant sections of the text before they come to your laboratory. The questions require minimal understanding of the concepts in the text and are a good preparation for the lectures as well as the laboratory. Students are required to score at least 70% to pass. If a student misses a question, the test is expanded to give them another chance to answer a similar question correctly. The more questions that the student misses, the longer the test. Student can take the check out as many times as they wish. They can use their textbook, their notes, and consult with other students when they take the check out. The important thing is that they come to lab prepared. When a student keeps getting the same question wrong even though they are sure they put in the right answer, it is almost never a computer glitch -- usually the student has an alternative conception. This is an excellent opportunity for instruction. Students' scores, questions missed, the number of times the check out is taken, and the time the student takes are all recorded in a file for your use. A student who has read the material with some understanding should pass the check out in less than 15 minutes. Of course, this rarely happens. Typically students read their text for the first time while they are taking the test, so they can take from 30 - 45 minutes to learn the information. If a student is taking more than 60 minutes to pass the test, this is probably too much time and you should discuss the problem with the student.

Why have team meetings?

To teach large classes as efficiently as possible, we divide the teaching responsibilities among members of a team. Some functions are best done by a lecturer in front of a large class, and some are best done with a small group. Because different people perform these functions, extensive communication is necessary. The presentation of a coherent picture of introductory physics to our students requires that the lectures, labs, and discussion sections be highly coordinated. There are usually several ways to present a topic in physics each with different notation, terminology, and emphasis. These different approaches, while interesting to the expert, are confusing for an introductory student. The team meetings serve to make sure that everyone knows and abides by the approach chosen for the class. The meetings should discuss the rationale for the class' "party line" until everyone feels that they know the reason for it and can enthusiastically support it to their students. Nothing is so demoralizing for the students than decisions which are not supported by all their instructors. Ideally coherence would be maintained by having every instructor visit every other instructor's class. Since this is not always possible, the team meetings serve this purpose.

Team meetings also allow the lecturer to discuss with the lab/discussion section instructors the pace and organization of the lectures and what the lecturer assumes that the students understand and can do. The lab/discussion section instructors discuss with the lecturer and among themselves the extent to which the students are understanding the material and which approach to teaching may help. Fast feedback is essential if this information is to influence the pacing and approach of the course. Of particular importance is detailed feedback from the grading of tests and lab reports. All instructors are encouraged to visit the lectures, discussion sections, and labs of other instructors as much as possible. The lecturer will visit your sections as much as possible and you should attend lecture whenever you can.

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Outline: General Plan for Teaching a Laboratory

NOTE: This and more information about teaching a Lab Session can be found at the TA Orientation link, in the Instructor's Handbook.

Opening Moves

Step 0: Be at the Classroom Early

When you get to the classroom, go in and lock the door, leaving your early students outside.  The best time for informal talks with students is after the lab!

•  Prepare the classroom by checking to see that there is no garbage around the room and that the proper equipment is on student tables and on the front table.  On the blackboards, provide space for each group to write their answers to the Warm-Up Questions you selected.  If you have changed groups, list or project the new groups and roles.  (Remember to follow the guidelines for forming groups and rotating roles in the Instructor's Handbook).

•  Let your students into the classroom when you are prepared to teach the lab.  To keep the students from collecting data before they discuss their answers to the Warm-Up Questions, set aside a small but necessary piece of equipment.  Pass this out only after the discussion is finished.  [After the students are used to the lab routine, you will not need set aside a piece of equipment.]

Step 1: Prepare Students for Group Work (~ 1 minute)

If students are working in the same groups, remind them to rotate roles. 

Step 2: Prepare Students for Lab (~ 15 - 20 minute)

a)   Focus on what students should learn (~ 1 minute).  Tell your students which Warm-Up Question(s) they should discuss and put on the board, and what aspect of problems solving they should learn in the lab.

b)   Diagnose student difficulties (~ 5 minutes).  While the students are discussing the assigned Warm-Up Questions, circulate around the class and observe/listen to all groups.  [Do not intervene with any group unless they have a simple clarification question.]  Try to diagnose the difficulties your groups are having coming to consensus on the answers to the warm-up question(s).  This is easier to do for some lab problems than others.

No matter how severe students' conceptual difficulties seem to be, DO NOT LECTURE about the physics concepts of the problem.  They have an opportunity to see the theory of physics in their lectures and textbooks, but lab gives them an opportunity to find out for themselves whether they are right about the way the world works.

Even if the lecturer has not yet covered the material (which happens occasionally), do not lecture the students about the concepts or lab procedures.  Some lab problems serve as good introductions to a topic, and need only minimal reading from the text for students to be able to complete the warm-up questions before the lab.  In other cases, you can treat the beginning of the lab like a discussion session.

c)   Posting group answers (~ 2 minutes).  Select one person from each group to write their group answers to the warm-up question(s) on the board. 

d)   Lead a class discussion (~ 10 minutes).  Many students can come up with reasonable looking graphs or a correct prediction equation for strange reasons that do not follow the accepted laws of physics.  If you do not discuss these reasons, your students will never realize later that their reasoning is incorrect.  The warm-up questions on the board give you an easy way to have students discuss the physics involved in solving the problem

(i) Give students a few minutes to read all the answers on the board.  Then ask the representatives of each group to give their reasons for each of their answers.  Ask questions about the similarities and differences in what’s on the board.  Do the differences reflect different physics, or different ways or representing the same physics?

DO NOT TELL THE STUDENTS WHETHER THEIR ANSWERS ARE CORRECT!  This would spoil the whole purpose of the labs.  Tell the students that at the end of the lab, they will be asked to write on the board any corrections to their warm-up questions.

(i) Discuss briefly the measurements they will make to check their prediction.  For quantitative problems, discuss the more direct measurement(s) of the target quantity as well as the measurements of the independent variables in the prediction equation.

e)   How Much Time (~ 1 minute).  Tell students how much time they have to check their prediction.  If you see from the class discussion that there are prevalent or varied alternative conceptions shown in students' group answers to the warm-up question(s), you will want to stop students earlier so that you can have a longer discussion of their ideas at the end of the lab problem.  If, on the other hand, students seem to understand the relevant physics reasonably well before they begin their laboratory problem, you will not need as much time for discussion.  The students should then be able to check their prediction very quickly.

 

Middle Game

There are three instructor actions during the middle game: coaching students in problem solving, grading journals, and preparing students for a whole class discussion.  You will spend most of this time coaching groups.

Step 3: Coach Groups in Problem Solving

Below is a brief outline of coaching groups.

a)   Diagnose initial difficulties with the Exploration.  Once the groups have settled into their task, spend about five minutes circulating and observing all groups.  Try not to explain anything (except trivial clarification) until you have observed all groups at least once.  This will allow you to determine if a whole-class intervention is necessary to clarify the task (e.g., “I noticed that very few groups are exploring the range of values for . . .  What do you think . . .”).

b)   Monitor groups and intervene to coach when necessary.  Establish a circulation pattern around the room.  Stop and observe each group to see what decisions they are making.  Don't spend a long time with any one group.  Keep well back from students' line of sight so they don't focus on you.  Make a mental note about which group needs the most help.  Intervene and coach the group that needs the most help.  If you spend a long time with this group, then circulate around the room again, noting which group needs the most help.  Keep repeating the cycle of (a) circulate and diagnose, (b) intervene and coach the group that needs the most help.

      If a group finishes early, check their conclusions before you let them start to work on the next assigned lab problem.

Step 4: Grade Lab Procedure

This should be easy and quick to do.  Check to see that your students are:

•  students spend adequate time completing the  Exploration;

•  a measurement plan is recorded in the journal before students begin making measurements;

•  observations/measurements are written in the journal;

•  data tables and graphs are made in the journal as the data is collected;

•  analysis is completed before students discuss conclusions;

•  conclusion includes answers to all questions AND a correct solution to the problem (if they did not answer the Warm-Up Questions correctly).

If, after a few reminders, a student (or group) is not following these procedures, then tell the student(s) that they have lost their journal point(s).  Losing a point once will prompt almost any student to improve his or her journal keeping.  [Losing one point will not jeopardize a student’s final lab grade for the course.]

In computer labs, not all analysis is completed on the computer.  Students should be taking data and writing down coefficients and equations as they analyze their data.

Step 5: Prepare Students for Class Discussion (~ 10 minutes)

a)   Ten-minute Warning.  Ten minutes before you want them to stop, tell students to find a good stopping place and clean up their area.  Make sure you have finished grading journals.  Also, pass out group-functioning forms at this time (as necessary, about every 2 - 3 weeks).

When you were an undergraduate, your laboratory instructor probably did not stop you to have a class discussion.  Doing this is one of the hardest things you will have to do as a TA.  You may be tempted to either let students keep working so that they can get as much done as possible, or to let them go home early so that they like you better.  But students do not learn from their laboratory experiences unless they are actively engaged in figuring out what they have learned (see Redish, 2003, page 163).

In the beginning, a few students may try to keep working.  If it is necessary, you can make obstinate students stop working by removing a small but essential piece of equipment (i.e., a battery or a connecting cable) so that they are forced to stop taking data.  You are in charge of the class, and if you make it clear that you want the students to stop, they will.

b)   Posting Corrected Warm-Up Questions.  Tell one person in each group to write their corrected answers to the warm-up questions on the board.

 

End Game (~ 10 - 20 minutes)

Step 6: Lead a Class Discussion (~10 minutes)

The whole-class discussion is always based on the groups, with individuals only acting as representatives of a group.  This avoids putting one student "on the spot."  The trick is to conduct a discussion about a specific aspect of problem solving without (a) telling the students the "right" answers or becoming the final "authority" for the right answers, and (b) without focusing on the "wrong" results of one group and making them feel stupid or resentful.  To avoid these pitfalls, start with general, open-ended questions.

• What is similar about the position versus time graphs?

• Which part represents the cart slowing down?  How can you tell that the cart is slowing down?

 

In the beginning of a course, students naturally do not want to answer questions.  They unconsciously play the waiting game: “If we wait long enough, the instructors will answer his/her own question and we won’t have to think.”  Try counting silently up to at least 30 after you have asked a question.  Usually students get so uncomfortable with the silence that

somebody speaks out.  If not, call on a group by number and role:  “Group 2 Skeptic, what do you think?”

After the general questions, you can become more specific.  Of course, the specific question you ask will depend on what your groups write/draw on the board.  For the rolling up and down an incline:

• What function represents how the position changes with time while the cart is slowing down?

• How can you estimate the constants in this function from the graph?

Remember to count silently up to 30, then call on a group if necessary.  Always encourage an individual to get help from other group members if he or she is "stuck."

Encourage groups to talk to each other by redirecting the discussion back to the groups.  For example, when a group reports their answer to a question, ask the rest of the class to comment:  "What do the rest of you think about that?"  This helps avoid the problem of you becoming the final "authority" for the right answer.

Step 7: Group Processing (as necessary, ~ 5 minutes)

An occasional whole-class discussion of group functioning is essential.  Students need to hear the difficulties other groups are having, discuss different ways to solve these difficulties, and receive feedback from you (see pages 42-43).  Randomly call on one member of from each group to report their group answer to the following questions:

• What is one difficulty your group encountered working together?

• What specific action did your group decide would help you work together better next time?

After each answer, ask the class for additional suggestions about ways to handle the difficulties.  Then add your own feedback from observing your groups (e.g., "I noticed that in some groups, one person is doing most of the work.  What might you do in your groups to avoid this?")

Step 8: Start Next Lab Problem

If there is time, have students start the next assigned lab problem.  Repeat Steps 1 through 7.

Step 9: End of Lab Session

a)   Tell students what lab problem(s) to solve for next week.  You will decide what lab problems all students should solve in your team meetings.

b)  Assign students problems to write up (if last session of Lab/topic).  Each student will write a lab report for one problem from each Lab/topic.  If there is one student in a group who was not participating as well as you would like in a particular problem, you might consider assigning that problem to the student.  This way either the group will help the student catch up with the important information, or the student will learn to participate in the future.  [A lower grade on one written lab report will not jeopardize a student’s lab grade for the course.]

c)   Leaving the Lab.  Leave a neat lab room for the next class.  Do NOT let the next group of students into the classroom.  Report all broken equipment to the lab coordinator by clicking on the LabHelp Problem Report Form on a computer desktop.