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Labs (and the Not So Obvious Use of Labs by Non Scientists)

By Ken Cheney
I am eager to learn from you, so please e-mail me your opinions!

  "If the experiment smells it’s chemistry, if it wiggles it’s biology, if it fails it’s physics."



What are Labs?

I consider labs to be any learning situation where the student is actively involved, in contrast to a pure lecture situation where the student passively adsorbs content provided by the teacher.   "Lectures" where students are actively asking and answering questions will even come under this definition, although I won't discuss them much here (See "Lecturing").  I will consider activities from sports to post doc. research!

Unfortunately, I have mostly discussed “experiments” with equipment.  Well, that is what I know best!  I believe there is a lot of overlap with training (e.g. planning, safety, practice, . . ), so I hope this will be of help to those doing “labs” that are not experimental.

Who am I talking to?

I visualize several possible audiences.  You might be an experienced teacher new to labs, someone experienced in labs but new to teaching, someone new to both labs and teaching, or (conceivably) someone experienced in both labs and teaching who is just hopeful of finding some ideas new to them.  I have strong opinions as to what "should" be taught in science labs in particular and in lab situations in general; I hope I will not offend all my readers all of the time.  If you are offended, I hope you will carefully consider why I am wrong (and let me know!)

As you will see, I feel labs are best taught by those experienced in doing the topic of the lab.  Of course in the real world this is not always (usually) possible.  If you want (or must) teach labs without practical experience, I hope some of my hints will prove useful.

Style and Presentation:

Following my own advice about presentation styles, I have written this essay informally in the first person with liberal use of personal examples and opinions. The reader should keep in mind that they are personal opinions; little is certain in education! My examples are, unfortunately, heavily weighed toward science. This selection simply reflects my experience, not my opinion that one field has a monopoly on good or bad practices.

The plan will be to cover the subject in a broad, shallow survey rather than by a deep focused analysis.

"My background in experiments and teaching:

  • I’ve taught Physics, Programming, Laser Technicians, driving (the family business) and gymnastics (three national champions used routines I taught them). 
  • I’ve originated or completely redesigned entire labs for laser technicians, computers for laser technicians and computer graphics.
  • I’ve designed almost fifty new individual labs for physics classes (never all used at the same time) and many more for lasers.
  • I’ve written manuals for labs for Physics majors, for Life Science majors, for Liberal Arts majors,  for Programming for Laser Technicians, for Fortran, and for Computer Graphics.
  • My professional experience in labs consisted of four years working in the aerospace industry (directing experiments in support of electric propulsion for spacecraft etc.) and a summer at JPL working in support of the solar simulator.
  • I'll discuss many aspects of teaching labs, all the way from surviving Murphy's Law to planning a complete lab course.

"Why do labs?  If you understand them there is no need to do them.  If you don’t understand them there is no point in doing them.”

"Ahhhh, but you just might learn by doing!!!!!!!!!"

What’s different about labs?

What can be done in labs better than in lectures?  Much research answers “everything”, but here are a few specifics.  Specifics for science labs are listed below!

  1. Training
  2. Teach professional attitudes
  3. Personal interaction with students. Learn their majors, past experience, plans for the future, . .
  4. Learning to distrust data!! And theory!!
  5. How to do sanity checks on data and theory
  6. How to deal with imperfection!
  7. Lab reports
  8. Experimental design
  9. Data analyses
  10. Training
  11. Students can develop confidence in their own ideas and abilities.
  12. Your students can learn many more real world tools than they could just listening to lectures.
  13. Morals for any type of lab:
  • Don’t give up!
  • Keep Thinking!
  • Do your best, and be proud of it.
  • Show class!
  • Keep your cool!

What’s fun about labs?

  • You can interact with students.
  • You can try different approaches to teaching and experimenting.  Lectures tend to leave you lecturing!
  • With much more time in a block, you can try class activities not practical in a one hour lecture section. 
  • Students can be creative.
  • Students can see their own ideas carried out!
  • Students can watch as their skills develop noticeably.

Types of labs:

Labs are taught in many disciplines and for many reasons.  There might seem to be little in common between football practice and labs being done by a biology post doc.  However these labs may have more in common than physics labs being carried out in adjacent rooms for Liberal Art students and for Physics majors. Let me discuss the objectives of various types of labs:

1. Training (vs. Education):

Perhaps the majority of "labs" are training in the sense that they are intended to install specific skills, either physical or mental.  This is in contrast to "education" where developing generalized skills and thought processes is the object.

Naturally, there is considerable overlap.  A welder should be able to generalize a bit to different pipe sizes, etc., while even a very sophisticated chemist needs good habits while working with toxic chemicals.

The teacher of a laboratory course probably should carefully consider what they desire to teach in the way of education or training.  It may be best to take a break from sophisticated considerations occasionally to master some of the tools of the experimentalist trade.  In the case of physics, experimentalists need to know how to use oscilloscopes, signal generators, interface computers, build simple amplifiers, etc.  These topics aren't (for this purpose) examples of electricity and magnetism but are simply tools of the trade.

On the other hand, training can be made more valuable by "education".  I suspect a welding instructor might occasionally take a break from the skills of welding to contrast other methods of fastening: gluing, bolts, rivets, . . . (not to mention the various kinds of welding: arc, gas, electron beam, . . .). This diversion is not to train experts in other techniques but to give the students a wider view so they may recognize when some other technique (or combination of techniques) is more appropriate - education!

2. Doing Research

In these labs the students are actually doing research to find out something new.  The research may not look fundamental to someone experienced in the field, but it is designed to be near the limits of the capabilities of the students involved.  A gymnast may be investigating how reliably she can do a new skill in a routine, or physics students may be investigating how wildly real friction differs from the textbook variety, but in any case they are exploring something unknown to them and, perhaps, to anyone. This type of lab exposes students to the joys and frustrations of the real world.  There is no guarantee of success, but what is learned is something the student can regard as their own achievement.

It might be thought that everything accessible to students was well understood by "the ancients," but once one is looking for them, there seem to be an unlimited number of small but interesting problems that are not well understood.  Of course research in a freshman class may not set these problems to rest, but here it is the journey not the destination that is important.

Of course everyone (students and teacher) must take the results with a grain of salt.  You probably wouldn't design a skyscraper based on the tests of welding techniques made in a welding class.  However the student welders who designed and executed the tests will have a much greater appreciation of what may or may not work as they see their welds fail under test loads.  Conversely the teacher shouldn't expect polished results (lack of time, materials, knowledge, .  . ). 

It’s the process that counts, not the product!

3. Historical Labs

These labs redo classical experiments, either following as closely as practical in the footsteps of the originator or using modern methods to achieve the same type of result.  Such reenactment can be very satisfying to students.  I, and many other physicists, fondly recall doing the Milliken Oil Drop Experiment (the first experiment to determine the charge on an electron).  Our experiments were not easy, clear cut, or accurate.  But, we had actually dealt with one of the fundamental experiments in all of physics!

These labs often can't realistically be considered training or education, but they are very important to the culture of the discipline!

4. Time Wasters (keeping the kids off the streets):

“Teach something!” Perhaps the greatest impediment to teaching is that students have learned from experience that most of school is simply useless stuff designed to keep them busy.  Figure out something really educational for the students to be doing! Student designed, researched, and executed labs are bound to be educational, but perhaps hard on the teacher!

5. Proving Theory:

For a scientist this is the most frightening type of lab of all!  Why? To claim that you are going to “prove” or even “verify” a theory is to strike at the very heart of science! 

Theories cannot be proved! Theories can be checked or disproved. The essence of science is that theories (if they are to be taken seriously) must make predictions that can be checked (be falsifiable).  The theories then should be checked.  Finally, most important, the theories that made wrong predictions are discarded, no matter how fond we are of them.

Theories surviving many attempts to disprove them are treated with more and more respect and used with more and more confidence.  Does this mean that the theories are "true"?  No, it just means they make predictions we can't disprove with our present accuracy of measurements.  In some fields, measurements are so crude that virtually any theory can be twisted to match the data (take theories of education for example).  In contrast, it is known, experimentally, that gravitational and inertial mass are the same to 1 part in 100000000000000000000 or so.  But it is not known that they are the same.  Physics is strewn with excellent theories (Newton's Mechanics, light as a wave, heat as a fluid, . . .) that work fine for most purposes but that fail in "extreme" cases.

The problem with "proof" is that we cannot try all possibilities, and we cannot measure to an infinite number of significant figures.  Therefore we can't be sure that the theory works perfectly in all cases. At best, we can say that for the conditions we tested, the results were within some percent of theory.  With a bit of statistics we can say what the probabilities are that this difference is significant (i.e. that our results probably disprove theory or that the difference between our results and theory is likely due to random errors).

To say a lab is to "prove a theory" is to miss a vital element of science!  We can check theory, we can disprove theory, we can not prove theory!

6. Hands on for the experience:

A type of lab that is very useful despite the fact that it is neither training nor (strictly) educational is the "play with the equipment and concepts" lab. Most people find it hard to visualize things that are just described or even pictured.  It generally helps a lot to have a personal experience with the objects or concepts. More, most people are delighted to find that they can actually operate an instrument, plot a graph, do a flip (sort of) even if not very well.  In the future when the student sees or hears of that activity they will say to themselves "I’ve done that and I know what its like!"

7. Reinforce theory by using it for real:

This type of lab can be a dull “follow the manual” experience or an exciting, creative activity.

8. “Follow the manual”:

The manual spells out in detail the steps to follow, the boxes to put the numbers in, and, perhaps, even the conclusion to draw. The apparent upsides to this approach are that the lab looks very organized, the students feel secure, the students have a good chance of “success”, and the lab is over quickly. The downside of this plan is the elimination of almost any chance of the students learning anything. 

"If your bubble never bursts you’re not pushing the envelope."

9. "Here are the tools and the problem, figure out for yourselves how to solve the problem”:

The upsides of this approach is that the students stand a very good chance of actually thinking about the tools (theoretical and mechanical) they have to work with.  Having devised ways to use these tools the students are almost certain to have gained a much better appreciation of what can be done.  Further, since a considerable amount of student thought has probably gone into the experiment, the odds are good that the students will retain much of their knowledge.

The downsides of this approach are that the lab appears quite disorganized and that many students will be uncomfortable as they are not told exactly what to do.  This lack of comfort can lead to many complaints and frustration with the lab. There is no doubt it is difficult for the teacher to judge precisely how much help to give to insure a good ratio of success to suicide. 

The students can’t be safely left on their own; they will mostly attempt impossible designs or not plan at all.  You must assign milestones that you have to approve, and you must regularly consult with the students as to how their design or experiment is going.  At least two weeks are required generally; the first week (if luck holds) eliminates many impossible devices leaving (you hope) workable devices for the second week!

Administrators and other teachers often haven’t a clue as to the point of such labs! It probably is a good idea to educate supervisors beforehand about the philosophy behind the lab design and the possibility of failure. 

Examples of “figure it out for yourself” labs:


When I was teaching programming I would generally present a programming tool, arrays say, give an example or two or their use, and assign the students to write a program about their interests using the new tool.  Students would generally get into the intricacies of their own problem and do much deeper work than they would have just solving a problem I assigned.


There is a powerful concept in physics called the conservation of angular momentum.  This is familiar to dancers and gymnasts who spin fast with their arms in close to their body and spin slowly with the arms outstretched.  I have many times assigned my physics lab the problem of designing an experiment to check this law.  Each group was to invent a different approach, then actually build and use their apparatus.  Students who had previously displayed little interest in the “canned” labs suddenly showed quite unexpected powers of creation as they developed their own strange and wonderful machines.  Not all the machines worked. (They didn’t have to work.  A good try and analysis led to a good grade.) But all the students received a great grounding in the conservation of angular momentum and in the perils of experimental design.

DigDig Deeper for an extensive list of what can be taught in science labs, and why such labs are important.

DigDig Deeper for thoughts on why labs should be taught by experimentalists.

Preparing for labs:

An ideal lab might have the following properties:

  • Surprises: Students will be more interested in labs that provide surprises.  The surprise could be in many forms: The results of an experiment (seen at once), the results of an analysis, the discovery by the students that they could do something they never expected to do, the “Ahhhh” moment when the students make a connection between theory and everyday life . . .
  • Transparency: The connection between the parts of the experiment and between the measurements and the conclusions should be easy to follow.  A great experiment that looks like a black box to the students is useless.
  • Extendability: The students should understand the method and equipment so well that they can apply the principles to other applications.
  • Student contributions to the design of their experiments: Students will learn much more, and develop more confidence, if they do part of the experimental design, the more the better.
  • Important topics: Are the topics important or just traditional?
  • Optimum experimental design: Is the method of doing the experiment the best for achieving goals, such as those listed here, or is it just the traditional design?
  • Involves general-purpose equipment: Are the tools the student learns about in this experiment going to be of general use to the student or are they specialized to this experiment?
  • Teaches tools of the trade: Does this experiment lend itself to teaching some necessary “tools of the trade”?  These tools may be safety checks, a critical attitude, oscilloscopes, safety around an imploding vacuum system, how to fall when you miss a catch in gymnastics, preparing beforehand, how to read manuals, or any of dozens of skills and attitudes necessary for success in life.
  • Appropriate Difficulty level: This can easily be a potent source of conflict between ambitious teachers, students, supervisors, and colleges! Naturally your baseline depends on your students' abilities and the purpose of the class: Liberal Arts Physics for Poets, Transfer to Caltech, training journeyman welders, preparing for MSATs, etc.
  • High but attainable standards:My students often complain: “but this is hard to do”, “…figure out”, “…debug”, etc.  I tell them : No one will pay them BIG BUCKS for doing easy things. Students seem to identify very well with this idea once it is pointed out to them! I’m an advocate of high, layered, standards.  Students will, generally, adapt to the standards expected of them if the expectations are attainable.  If the expectations are low the students will learn little, be unprepared for future courses or jobs, and, worse, expect life to continue giving them a free ride.
  • Requirements that can be layered:  There can be minimum requirements for everyone (“C”) and suggestions or requirements for better grades.  For example, it may be enough to take some plausible data and do some analysis to get a C.  To get an A all parts of the write up should be good but, more important, the results should be examined and any interesting points discussed.

    I tell my students that pointing out the interesting points is enough, they don’t necessarily have to explain these points (no one understands everything).  However, I claim that at Caltech these aberrations would be the start of the experiment, not the end!

Foolproof (low expectation) labs:

The opposite end of the difficulty spectrum is to design (buy!) labs that cannot fail and require almost no analysis.  This type of lab will meet with little resistance from most students or supervisors.  For labs offered for cultural purposes (Art appreciation, Physics for Poets) this approach may be quite suitable.

What do you want to teach? How deeply? Even after the most careful preparation, you should expect to make many modifications as the result of your experiences with the class, department, and school.

Why are the students taking the course? What do they need to do with the knowledge they gain? Live a fuller life, vote intelligently, run an auto repair shop, pass a MSAT, go to graduate school in your discipline, . . .

What is the background of your students? Right out of high school, still in high school, returning students, majors in your discipline, majors in auto shop. . . Students who know something (i.e. have lived a little) are MUCH easier to teach than students straight from high school who carefully avoided actually learning anything!

  • What are their native languages?
  • Do they understand English? Spoken? Written? How well can they write?
  • Do they have the background necessary for your course? Math? English skills? Maturity? Motivation? . . .


  • How much do the students already know?
  • How much must the students know?  About the equipment, about the theory?
  • How much would you like the students to know by the end of the experiment?  About the equipment, about the theory?


  • Are there “tricks of the trade” that you can teach here  (e.g. laser safety, how to spot skills in gymnastics, how to unplug a power chord . . .)?
  • Are there features of experimental design to be taught here?  e.g. controls, clamps (for safety), avoiding systematic errors . . .

Practice, Practice, Practice

Murphy never Rests

Check lists: Preparing for a lab – survival and success

What equipment is to be used?
Can you make the equipment work? 
What can you think of that the students can do to make the equipment fail?
Is there enough equipment for each student / group?
Does all the equipment work?
Are there quirks to the equipment that you and the students should be aware of?
Are the manufactures’ manuals available?
Are detailed instructions or check lists available for this experiment?
Can you study good student reports?
Can you audit an experienced teacher’s class?
Can you consult with an experienced teacher about quirks of the experiment, good methods to present the experiment, things the students often get wrong, . . .?

What do you do during the lab? Beware of Lecturing!!

Students want to get their hands on the equipment.  Tell them just enough so they are safe and can do something then let them start.  After a few minutes they will realize they don’t know everything (but they will know lots more about the experiment then they did originally) and will be much more receptive to your hints and suggestions for further investigation.

Have a minimum of talk, a maximum of discovery!

"But what do we do?” It is disheartening to hear this question just after two hours of brilliant lecturing on what they should do.  Life is better for you and the students if you feed them the information five or ten minutes at a time with hands on work in between.  Have micro lectures several times during the lab.

About lecturing: Methods of presenting the material and involving the class

"Tell, Tell, Tell:" The advice of the U.S. Army to teachers is "Tell them what you are going to tell them, Tell them, Tell them what you told them." Good advice.  But, telling is not as good as showing, and showing is not as good as doing.

Methods of presenting the material and involving the class

Tell what you are going to "teach" today.

This will help greatly in keeping the audience oriented. Listeners often have trouble separating the point of the lecture from the surroundings (i.e. they can’t tell the steak from the sizzle unless you help them).

Tell why the audience should care!

Everyone pays more attention if they know the knowledge they are about to acquire will help their health or happiness (i.e. "Your chances of having cancer will be reduced by 30% if you follow these food guidelines").

What applications can you include?

The more real world (or philosophical) applications you can reference, the more likely it is that the audience will identify with your point.

What are amusing parts?

About grammar: "Piano for sale by lady with mahogany legs"

Is there some interesting history to the ideas?


What questions can you ask the class to force them to actually use the concept?

After outlining the classic plot of Romeo and Juliet, you can ask: "How many movies or plays do you know that are takeoffs on Shakespeare’s Romeo and Juliet."  Or, after defining "amplifiers" ask what political, social, mechanical, and religious mechanisms fit the definition of amplification.

Can you ask questions leading the class to discover the concept for themselves (Socratic method)?

This works great for the students who participate. I suspect it doesn’t do much for the students who are waiting to be told "THE ANSWER".

Can you demonstrate the concept?

With a demonstration, with the aid of the class, with slides, with movies, with videos, over the web...

Can students do part of the presentation?

Generally student presentations are technically awful (not always, some easily put professional teachers to shame), but they may more than make up with empathy what they lack in gloss.

Can you connect the concept to an overall theme of the lecture?

Everyone learns items best that are connected in their mind. If the lecture has a theme to connect the parts, students may easily remember otherwise disconnected and arbitrary items. The theme doesn’t even have to be "correct", just mnemonic (e.g. taken alone, "Animal Farm" appears to be just a series of amusing and horrifying incidents. Taken as an analogy to the effect of Communism on a country, the outrages follow history and necessity like clockwork).

Can you connect the lecture to the overall theme of the course?

Keep checking how the class as a whole is doing: For example: “Has anyone got any data yet?”, “What percent errors has anyone got?”, “Jane found that there is less friction if you . . . “, “Did you remember to level the equipment before taking data????”

About note taking!   Don’t expect much.  Strange!  Stranger yet, students generally only take notes by copying what you put on the chalkboard, completely ignoring all the clever hints you give vocally.  My daughter suggests you write: “Take notes of what I say.” on the board.  Have the equipment for the students to handle as you explain / demonstrate. Ask the students to find and explain the parts. Demonstrate some functions, then give the students time to emulate you.  Leave your setup working for the students to examine.  Don’t expect the students to remember long, detailed explanations.

Have next week’s lab set up for the students to examine. Have the students put their results on the chalkboard as they progress.  Then everyone can see what is reasonable, what averages are, perhaps compete for the “best” results.

White Board:  Have the students do their calculations on a large (12” by 18” say) smooth white board.  They can write with dry erase pens intended for classroom white boards.  With these large calculations everyone in the group (and you) can easily see what is going on.

Checklist of milestones during the lab:

You have checked that the setups look reasonable.
Equipment has been safely turned on
 The equipment responds (right or wrong).
 The equipment responds correctly.
Some data is obtained and plotted.
The students do a “sanity check” with their results. I.e. the results look plausible. 
While the students work you walk around and:
Discuss what is happening:  What the students have found interesting or puzzling, What you can draw their attention to, . . .
 Insist they do things more or less correctly!
 Initial their results when the results look reasonable.

Lab reports and consulting: What do you and the students do after the lab? 

Why lab reports?

No experiment is a complete waste.  It can always be used as a bad example. But, if the experiment is not reported, or the report is unintelligible, even the most brilliant experiment was a complete waste. If you can't stop a passerby on the street and explain your experiment then you don't really understand it yourself. Most students and many professionals would prefer a root canal to sitting down to write a report on an experiment.   Many teachers feel that time spent in report writing is time taken away from the experiment.  "The students can learn about report writing in a later course." In contrast to some of these views I feel it is never too early to start learning about reporting results; in fact reporting is an integral part of doing and learning from an experiment.

  •  First, if report writing is put off until "some later course" the student may never be forced to learn how to write reports at all!
  • Second, it is probable that the student doesn't really understand the experiment if they can't produce a lucid description of what was done and why it was done that way.  There is a fair chance that in trying to explain what happened, the student will deepen their own understanding and become aware of aspects of the procedure or results that would otherwise have escaped notice.
  • Third, if there are questions later as to just what did happen, it is vital that the report contain the necessary information: equipment, dimensions, procedures, details of the analysis,. . . . .   .  If anything interesting is found there are always questions.
  • Ultimately perhaps most important to any professional is that progress in their field depends dissemination of the test results (or what people know about your work).  There are no Nobel Prizes for unpublished work.  There is no long employment for even the most brilliant researcher if no one in the company can understand their reports.

Length and time for lab reports: There are limits as to how much time students can be expected to (or should, considering that they may have a life outside the physics lab) spend on report writing.  It seems to me that most of the time should be spent in thinking and not in the mechanics of producing the report, so shorter thoughtful reports should be encouraged over long, rambling, pointless reports.  (e.g. untouched computer printout.)  Many students have a great deal of trouble distinguishing between the value of polish and volume in contrast to thoughtfulness.  Considering what sells, this confusion is quite reasonable.

Work finished in the lab:Much of the report can be done in lab if slightly sloppy (but clear enough) work is acceptable.  Equipment lists, sketches giving dimensions, data tables, many plots, and a preliminary conclusion can be prepared during the lab.  

Initialing parts of labs as they are done:  If you insist on initialing a rough draft of the conclusion during lab, you can often assure that the students are headed in the right direction and at least understand the point of the lab!  If the conclusion is at odd with reality (or the student's data), you can encourage them to rethink what they are saying.  With the equipment still available to check again, many otherwise hopeless results can be saved by locating faulty measurements, bad readings, misreported data, etc.  This, finally, reinforces one of the vital lessons to be learned by doing labs:

"Trust nothing! - Check!  Check!  Check!"

During the week consulting: Encouraging students to check with you during the week before handing in labs can be very rewarding.  I tell my students that before the lab is handed in my advice is free, after the lab is handed in my advice, if needed, will be paid for with lower grades.  Discussing labs before they are handed can result in much lower stress (for the student) since they are just trying to see if they have the correct idea and are not being told they handed in something WRONG.  You can communicate much better with the students in this informal session than by exchanging reports and written complaints on the reports.  You can see how puzzled the students look and they can easily ask for more explanation, examples...

Content of lab reports:

The Procedure section in reports: In contrast to scientific writing constrained by the space constraints of journals, it is very useful to encourage students to present their procedure in a narrative form describing the motivation for procedures, wrong turns, cures, successes, failures, puzzles, etc.  The fact is that this narrative type of presentation is much more useful to anyone planning to repeat the experiment than a cold, perfect description of the final "successful" procedure.  This narrative also gives you, the teacher, much more confidence that the students were actually there and thinking while the experiment was done.  

"Interesting" results:  I emphasize to my students that for class purposes an interesting failed experiment is better than a dull (straightforward) experiment.  One of my more perceptive students pointed out to me that it was actually better to get weird results because they gave an opportunity for interesting analysis while the "correct" results didn't leave anything to talk about in the report.

"Correct Results": Students have undoubtedly been taught in other courses that they will be rewarded for reporting the "correct" results (irrespective of what actually happened).  It is generally a considerable cultural shift to convince the students that they will be rewarded for reporting the actual results.  

Of course the students with "interesting" results must also recognize that the results are noteworthy and try to analyze the implications.  Students should be encouraged by being told that the interesting parts of science are the parts that we can't explain yet.  Within the limits of a school lab (or, indeed, the real world) there is no shame in not being able to explain all interesting results. However, unexpected results that are not even recognized by the student as weird are a red flag to the teacher showing that the student doesn't know what they are doing and should not be released upon the world.  For example a lever that gives out more work than is put in should be treated with great suspicion.

What data to report?:

Students (like professional scientists) regularly take data until they get the “correct” result, then they stop and report only the data that gives the “correct” result.  Of course there is no point in reporting data that resulted from flawed procedures in a professional report.  (Actually it probably would be useful to report, as I suggest below, but journals now have little space for such niceties.)

However in a student report it is very helpful if the students report what they tried, what went wrong, and what they did to solve the problems.  This narrative shows that the students actually did the experiment and that they were thinking about the results!  I tell them that if they give it a good try and produce an intelligent report, they can get a fine grade with impossible data.  Further, if I learn about common problems, I can warn students so they can avoid these problems in the future.

Returning labs for a better grade.

If lab reports can be a dialog between the teacher and student, rather than a one-way street, the students can learn from their mistakes and get a grade commensurate with their new knowledge. I encourage students to return improved reports within a week after I return the graded and marked reports to them.  There is no limit on how high the final grade can be: D- to A+ is wonderful.

To keep the work to a minimum for the students and myself, I hand out the following rules:

Checklist for returning labs for a better grade


Labs must be returned to the teacher the next meeting after they are returned to you.
There must be a significant improvement, or attempt at improvement, on the items listed by the teacher.  No improvement, no more returns.
Write the date you are returning the lab.  i.e. "Returned 10/3/03"
Explain how to find the changes (e.g. "in green ink", "on pages 1-3", "circled", "on pages labeled NEW")
Fix what the teacher complained about first, then make other changes if you want.
You generally do not have to redo everything, just the faulty parts, reuse the good parts.
Include the original report, particularly the original list of problems.
If you write the report on a word processor show the changed or new parts in a different type, e.g. italics or boldface.
The finished report must be arranged in the proper order; add your changes in the logical places.


Murphy's Law: The fundamental law of experimental science: "Anything that can go wrong will go wrong."

Corollary one: "And, at the worst possible moment."

This law is best exemplified by Murphy's tragic death.  He was visiting London where American visitors often get in trouble because, from habit,  they look for traffic to their left when they cross a road.  Murphy however remembered to look to the right where British traffic would be approaching.  He saw nothing to his right, started across the street, and was struck dead by an American tourist driving down the wrong side of the road!

Some of the equipment doesn’t work (one group):

Usually, luckily, the equipment doesn’t work because the student forgot to plug it in, forgot to turn it on, . . .  Insist that the students call you over to check the equipment before they take it apart and replace it with other equipment.  Usually you can fix the problem with a click or two.

Check list for debugging one piece of equipment

Is there a power light on?

Does anything change when you turn the knobs?

Are the knobs in a foolproof setting ( i.e. the simplest possible setting)?

Are the knobs set the same as some similar equipment that is working?

If you exchange the item with a working item, do things work better?

If you put the suspected item in a working setup, do things still work?

Don’t forget, even wires go bad but look good!

It  still doesn’t work??  Replace it with another if you have spares.

If you don’t have spare equipment, you can let the students join another group.

Check list for “None of the equipment in the class works”

Check  for universal cures.  e.g. is all the power in the room turned off?
Perhaps everyone is following the same bad advice – some student’s, yours, or even the lab manual’s.  Rip one of the set ups completely apart and put it back together yourself.
The students may not realize how carefully they must follow the instructions to get the experiment to work.  Stop everyone and emphasize the importance of following instructions.
Nothing has worked yet?  Change to a lab on debugging!
Still nothing?  Change to a lab you can do with some equipment that works.
If the concept is really important, change to a two week lab and try, desperately, to get things working by the next week!
Change the lab to “extra credit” for the best attempts to make it work.

Check list for “Everything seems to work, but the results are wrong (for the whole class)"

Regard this as not as a problem but as an opportunity to teach about debugging!

Point out the virtue of checking the results as you go!
Ask the class why the results look wrong.
Ask the class what could be causing the problem. 
Do some brainstorming for likely to wildly improbable causes.  Almost anything may eventually turn out to be the problem.  Be sure to include bad data, bad calculations, and bad theory!  Often everyone is copying an incorrect procedure or calculation!  See if the class can figure it out.
Write calculations out on the board with the help of the class.  Beware of mixed units! ( e.g. If one dimension is much larger than another, it is very easy to measure one in meters and the other in mm!)
Can you find some stage (from initial measurements to final conclusion) where the data looks ok?  If so, you can work toward the end and usually find where things went wrong.

Check list for wrong results for just one group:

Congratulate them for checking.
See if the data looks plausible.
Examine their NEAT calculations and sketch to see if they were going at it correctly.
Still looks ok?  Have different members of the group make the measurements.
Still won’t work?  Have them compare their data with the data of a group that got reasonable results to see if there are any gross differences.

Checklist for common problems:

Measuring the wrong thing
The instruments were read incorrectly (e.g. oscilloscopes are labeled in volts/interval but the user is supposed to know that it is the large intervals that count, not the small ones!)
A “Sanity Check” can eliminate some errors (i.e. having the students measure some known quantity).  For voltage measurements, a flashlight battery has about 1.5 volts.  If the measurement is 15 volts, there is clearly some error.  Varner calipers can measure one centimeter on a meter stick, . . .
Instruments may not be set to give calibrated results.
The range buttons on instruments may not be understood.  Try a sanity check.
The students don’t notice or don’t know the meaning of multipliers such as mu (millionth), m (thousandth), etc.

Download an editable Word version of the checklist.

Remember Murphy’s Corollary for debugging:

“The part that absolutely, certainly, positively can’t go wrong, will”


Safety for the students and public:

What aspects of the experiment can harm students or the public?  I.e. laser light, falling objects, dangerous advice, . . .

How can you minimize the possibility of harm?

  • Use safer equipment (e.g. many schools are using electronic thermometers in place of the traditional mercury in glass thermometers to avoid the danger of broken glass and mercury exposure).
  • Use the minimum voltage, current, temperature, speed, etc. that will make the experiment work.  We have several experiments that require high voltages that the students could easily touch.  We give safety instructions of course, but the saving grace is that the high voltage supplies produce only a very small current.  At worse the student (or teacher) gets an unpleasant shock but does not end up dead.
  • Redesign the physical set up (e.g. to keep laser light out of the student’s eyes we keep the lasers at waist level).      
  • Train the students in safe practices.  This takes time and repetition.

    Perspective: When I taught driving, many of the students were teenagers just old enough to get their license.  They learned very quickly, in fact this was actually a problem!  The typical teenager could do everything necessary to pass the test for their license with about ten hours of instruction.  Unfortunately this short time meant they had not spent much time on the road and had not encountered many of the emergencies that must be dealt with while driving.  If the student got their license at once, as seemed logical to them, they would have to learn to deal with these emergencies on their own with no instructor to look out for them. Within the family we made sure the teenagers had at least fifty hours of instruction (or at least practice with a licensed driver) before they set out driving on their own. This seems to be the law now in California.

    In the lab, for example one using lasers, it is necessary to not only tell the students what good safety practices are, but to continually walk around and see that the students are not looking into the lasers, aren’t putting their heads at laser level, aren’t putting the lasers at eye level, aren’t (accidentally usually) pointing the lasers out into the hall to zap people passing by, that they do have something in place to block the laser if it gets past their experiment, that they close the shutter on the laser to block the light when the laser isn’t being used temporarily, etc.  You have to continually check on these things, not just once but every time the lasers are used and every hour or so during the class!

Know how to phone for help. 

Be sure there is a phone available.  If there is no wired phone a cell phone, may well be worth considering.

Be sure who you will get when you dial 911.  On our campus 911 gets us campus security, not the paramedics etc. that we might expect.

Safety for the equipment:

Experience is directly proportional to equipment ruined.

When you are worrying about risking expensive equipment with students, it may help you to reason that one justification for schools is that by the time students are unleashed on the world the students will have already had lots of experience “trying” to destroy equipment and will therefore be less likely to destroy rare and vital equipment at their new job.

Expect that, despite the best of instruction, students will connect and adjust equipment in any way that is physically possible, and in ways you could have sworn were not physically possible. For your sanity the equipment must be able to withstand whatever may happen to it.

However, you can insist that fragile equipment (e.g. lasers) not be balanced on shaky stacks of textbooks and lab jacks.  If equipment must be raised, show the students how to make sturdy stands.  If necessary you can buy or build the parts necessary to keep the equipment safe.  I feel that it is good training for the students to design and build as much of the equipment as possible within the limits of time and skill.  The students will then have a much better appreciation of the function of the equipment and the challenges and opportunities of engineering.

Sometimes it will be necessary to physically bolt down equipment so it won’t be brushed onto the floor (e.g. computer monitors on carts). Electrical connections to equipment on carts are an invitation to disaster.  If equipment on a cart is plugged into the wall, it is inevitable that someone will move the cart without unplugging the wires and drag the equipment onto the floor.  We bolt a strip of plugs to the cart and plug it into the wall, and then we plug the equipment on the cart into this secured strip of plugs.

About waiting for instructions:

Whenever the class gets equipment new to them I ask “What is the most important thing to do when you first get equipment?”  I’ll get a variety of responses, mostly reasonable such as “plug it in”, “read the manual”, etc.  I then tell them the most important thing to do with new equipment is:

Don’t touch it until you get instructions! - The class laughs, but they often remember too!

Broken Equipment:

Equipment eventually fails on its own, so one doesn’t want to blame students for the “natural” death of equipment.  On the other hand, students should feel responsible for ignoring instructions and destroying equipment.

We have had good luck with the following rules:

  • If the equipment is broken when the students get it, the students are not responsible.  As soon as possible after receiving instructions, students should check that the equipment works.
  • If the students bring back the equipment, as “it doesn’t work” at the beginning of the class, we explain we will figure the equipment was broken when we gave it to the students.
  • However, if the students bring back the equipment as broken at the end of class we may well figure they broke it.
  • If, as far as we can tell the students were following instructions when the equipment died, we will assume a natural death.
  • Finally, if the equipment dies because the students were not following instructions, the students are responsible for replacing the damaged equipment.  Actually, we have never had a student destroy a thousand dollar oscilloscope by dropping it, or frying it with high voltage; perhaps our threats have worked.

You might want to look at the debugging section here, which gives hints on how you and the students can check whether the equipment really is bad.

Equipment: The need for the latest and greatest

Training yes!

If you are training students to go out to industry and immediately start to work, it is vital to have current equipment.  It is simply misleading to students to train them on obsolete equipment.

Education no!

However if the object is education, equipment is very secondary to the design and philosophy of the course.  Properly educated students may not know exactly how the latest gismos work, but the students do know what is possible, what is necessary, what to ask, and how to educate themselves about the latest details.

Desperate circumstances:

Often in the real world one must make do with what is available.  If training must be done and good equipment isn’t available, wonders can be done with what appears to be unsuitable equipment.

Of course you must let the students know what the situation is: “This equipment isn’t the real stuff, but you will learn the principles so you will know what is going on when you get the real stuff.”

Perspective: The most spectacular example I have been associated with was conducting a program for Laser Technicians before we had any lasers.  What we didn’t have we simulated.  Instead of doing interference experiments with lasers, we did them with water, sound or microwaves.  Instead of commercial lens testers we made crude ones out of fiberboard and cardboard.  Surprisingly, the students were the most successful students we ever had.  Education instead of training perhaps?

Equipment overkill, or why you might not really want that fancy equipment you could buy with that new grant:

The point to keep in mind is that, aside for training for specific equipment, education requires that the students completely understand what they are doing and be able to generalize it to other situations.  Often this means (as far as equipment goes) ”simpler is better”. On one end of the spectrum is a spectrometer that students construct themselves with meter sticks, clamps, lights, and a prism.  There are few parts, and all the parts are right out in the open to see and manipulate. On the other extreme is a computerized spectrometer that just requires the push of a button to calibrate itself, take a spectrum, and plot the results.  It might even do a fast Fourier transform to process the data!

For 99.99 percent of the students, using the crude spectrometer will lead to much greater understanding!  The other 0.01 percent of the students are at Caltech or MIT and don’t need us anyway.  Even the 0.01 percent student will probably have fun improving the crude spectrometer!

Computers have been a mild curse in the educational equipment market.  Once a computer is available, it is overwhelmingly tempting for the programmers to have the computer do all the amazing things computers can do, leaving mere humans in its dust.  This is great if you are using the data for research, but isn’t so hot if you want students to understand what is happening and why.

A Faustian bargain?

Modern equipment steadily becomes faster, more sensitive, more rugged, and easier to use.  Many effects that for generations had been the stuff of blackboards are now easy to do experimentally in a clear, elegant fashion.  Unfortunately, in some cases the experiments may be more clear and elegant to the teacher than to the students.  If the students only see “black boxes” that produce incomprehensible numbers by mysterious means we haven’t achieved much education.

On the other hand, often the sensitivity or speed of more modern equipment permit good measurements of phenomena that previously gave untrustworthy results (because we were working on the ragged edge of the capabilities of the equipment).  Now we have results that are much easier for the students to understand.  In the nature of things (some corollary of Murphy’s law) the most interesting effects are always just beyond our current capabilities.

If we are blessed with new, expensive equipment and computer programs we may be teaching the students to depend on tools that they and an ordinary company will not be able to afford.  It is good to always consider using programs that are widely available and to teach with industry standard types of equipment.

Perspective: This was recently brought home to me when I proudly sent an uncle (a retired math teacher) a set of Microsoft Excel programs I had written (for doing non linear least squares curve fitting) with hyperlinks to a Microsoft Word help file.  He e-mailed back that he owned neither Word nor Excel but had been able to try them out at the local library!  Although all the computers at the school may have certain programs not everyone in the real world does.  It’s probably safest to assume that your readers may have only a web browser.  Those with the time and talent to write programs in Java can pass them on to everyone with a browser, the rest of us are more constrained. I feel, strongly, that becoming familiar with industry standard programs and equipment and using it to build up many different experiments is immensely better for students using for each experiment special purpose programs and equipment (which will never be seen again) .

In the real world (outside of government boondoggles) one makes do with what equipment is available.  To paraphrase the army saying: "A good experiment today will always beat a perfect experiment tomorrow."

Students, given a good example, will soon learn to improvise with the equipment available instead of whining for newer, better equipment. It’s worth repeating:

No one will pay them BIG BUCKS for doing easy things.

Lab Manuals

Lab manuals are a puzzle.  Before we had manuals for most of our courses, we often heard the reasonable complaint from students that “How can we prepare when there is no lab manual?” .  After we (I) wrote manuals incorporating most of the items below, did the students gratefully drink in the knowledge presented in the manuals?  Guess!!

Still, lab manuals can have many vital and enriching types of content:

  • Necessary items: Clearly, manuals must provide the necessary facts that otherwise are unavailable or are only available in awkward and scattered sources.  These facts may include necessary numbers, instructions on the use of the equipment and programs, warnings of dangerous aspects to the experiment (dangerous to the student or to the equipment), . . .
  • Follow the steps instructions: The manual might include step-by-step directions for the conduct of the “experiment” and analysis of the results.  Remember the importance of training.
  • Culture:The manual might include historical, cultural, and application background to make the experiment more meaningful in a broad context.
  • Motivation: The manual might try to motivate the experiment by explaining why it is significant and how it is the basis for further developments.
  • Experimental nuances:The manual might point out some of the many experimental nuances that motivate this particular design and analysis.
  • Analysis instructions:The manual should indicate at least the minimal analysis expected to be made of the results of the experiment.
  • Further considerations:The manual could suggest further features that could be explored experimentally or in the analysis.
  • Pre lab preparation:The manual  could suggest the preparation required of the students before the lab.
  • Questions:The manual could have questions for the students to answer before or after the lab.
  • “Fill in the blanks”: The manual may provide “fill in the blanks”:  Tables, “complete this sentence”, Blank graphs, . . .
  • Reality: Many (most) students will (if they can) ignore the manual completely, if they buy it at all.
  • Solution: When you find the solution please let me know!

    Perspective: Skeleton from Caltech (in charge of the lower division physics labs at the time) told me they require the students to hand in answers to a few simple questions about the labs before the start of lab. You can give a simple test at the start of lab based on the manual and what you may have told the students about the lab the week before. I often make a bet with my class that if every student is ready (manual opened to the proper experiment and paper ready to take notes) at the start of class I will give everyone an extra letter grade (e.g. B goes to A) for the day’s experiment.  In some classes this leads to peer pressure to be ready at the start of class.  For most classes however I never have to pay off; never is everyone prepared!

“Modern formats for lab manuals”  CDs and Web based:

There are several attractive aspects to offering lab manuals on the web or on CD.  The content can easily include pictures, sound, and motion.  If the content is on the web it is “easy” to update instantly, in contrast to printed manuals or CDs. Downsides to computer-based manuals would seem to be that the “manual” may not be available in lab, or indeed the many places students may study.  It may also be hard for students to make notes to themselves on CDs or web sites! A very appealing upside of web-based material could eventually be worldwide sharing of material.  It is very appealing to think of simply linking to a site with a splendid explanation of the standard deviation of the mean rather than laboriously trying to reinvent this (very tricky) wheel.

How to get ideas for lab topics, procedures, and equipment

The following sources may provide good ideas (most of these sources will provide rather “bare bones” manuals with little motivation, history, tools of the trade):

  • Commercial lab manuals: Generally not great but tolerable!
  • Free (or almost free) lab handouts from equipment manufactures: Usually quite good for using the manufacture’s equipment.
  • String and sealing wax” manuals for grammar school: There are many books of these experiments; many are really splendid.
  • Do it yourself: Good but time consuming!
  • Teacher’s journals: Your teacher’s journals may have many generations of fascinating suggestions.  The main problem is finding time to digest all the great ideas.
  • Challenge the students to invent and develop the lab: These are the best labs of all, fun for students and teachers.  Many of our labs evolved over many generations of student improvements and inventions. The downside is that the teacher must be constantly involved to head off dead end plans.

What is a successful lab?

Scheduling of lab topics – lecture or lab first?

For an individual, useful knowledge evidently develops in two complementary ways. On the one hand a broad overview (world view or theory) can suggest expansions of the known facts to new possibilities that are tested by experiments.  If successful, these new “facts” are easily incorporated into the student’s existing worldview. If the learner’s original worldview is incorrect, then (experiments in learning show) considerable concrete, factual evidence must be adsorbed before the worldview can be corrected. In contrast, if the learner has no preconceptions (no existing worldview on this subject) concrete observations may gradually be incorporated into a cohesive worldview.  Both procedures seem valid and necessary.

Theories of learning seem to favor the first plan (incorporate new “facts” into existing mental structures).  However almost all experiments in learning physics seem to imply that it is necessary to have concrete (hands on) examples in order to build up a useful (problem solving in this case) worldview.

So, there are justifications for presenting concepts first as theories, presumably in lecture, or presenting the concepts first as the results of experiments that the students experience for themselves in lab. Strangely, students seem to feel that a topic is not real until it is presented in lecture, even if they have the same teacher for lecture and lab.         

One might think that “success” would be easy to identify, but it is often in the eye of the beholder. 

  • To the student: Consider the opinions of two typical students (stolen from Galileo’s writing) explaining why their labs were good labs.
    • During the lab: Salviati: I learned lots of good stuff and had fun doing it. Simplicio: We got out early and didn’t have much of a write up.
    • During the semester:Salviati: I find I am learning lots about analysis, professional behavior, and report writing.  My grades reflect what I have learned.  The teacher really cares and goes out of his/her way to help me learn. Simplicio: I’m getting good grades without much work.
    • During following courses:Salviati: This stuff I learned in that lab (yours) really puts me ahead of students from other schools. Simplicio: Why aren’t I doing as well as I did in that easy lab (yours)?
    • During their career: Salviati: All those lab and professional techniques I learned in that lab (yours) keep paying off. Simplicio: Well, that lab (yours) was the last easy thing I ever had.
  • To the teacher: Depends, I’ll generally go along with Salviati.  It is also nice if your peers appreciate what your labs are doing for the students.
  • Administrators: Varies.  Sometimes “Wow, we even have a good reputation at Harvard” at other times “The students never complain.”
  • Parents: I got my money’s worth from that lab, my daughter really learned a lot of useful stuff.
  • The Community: We are getting our money’s worth.  Our students are encouraged, do well when they transfer or get jobs and are taught good moral principles as part of their professional training.
  • Transfer Institutions: Great, students from ------------ do better than our native students.  (Don’t laugh, this is true in many instances.)
  • Professional groups (Unions, Nurses, etc.): Students from ------------ really know their stuff, they almost always pass our tests and have good, professional attitudes and habits.

Good bye, Good luck, Have fun!


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