The Do’s & Don’ts of Demos Some Guidelines Dean Hudek Brown University

Acknowledgements Jerry Zani - Manager of Demonstrations Robert Pelcovits, - Professor of Physics James Valles, Jr. - Professor of Physics

How I Came Up With This 5 years, U of I, Demo manager 15 years, Brown U, Director of Instructional Labs Perform complicated demos in class Give popular demo shows. Former Chair of AAPT’s Committee on Apparatus.

#1 A.Do make demos big enough, or adequately project them to be easily visible from the far reaches of the room. Do visibility tests – before class; ask someone to sit in several locations around the room and verify that the phenomena can be easily seen and/or heard. B.Don’t make demos too big – this can be a waste of resources and storage space plus the demo will probably be more difficult to work with so it is less likely to get used. C.E.g. 12’ x 3’x 3’ wave machine (on the floor), 7’x7’x3’ resonant pendulum frame w/ bowling ball.

#2 A.Do rehearse; it is important to be perceived as knowing what you are doing. B.Don’t stumble through the demo at the last second and risk botching it. This tells the students the demo is not important and you may even end up confusing them. C.E.g. Breaking Glass w/ sound etc. – know your frequency, your scope controls etc.

#3 A.Do use safe laboratory practice – students learn more by example than they do by words. B.Don’t take safety short cuts and then tell the students “don’t do that” – the students will learn “obviously someone who knows what they are doing does not need to bother with safety.” C.E.g. This is particularly true when working with acids, cryogens, high voltages, or loud noises (Big Cap Bang).

#4 A.Do use demos to introduce new concepts. Keep it simple – only introduce one new concept at a time, focus on the concept alone at first (equations will come later), make the apparatus as straight forward as possible, and only tell the students what they need to know to understand the concept. B.Don’t present several new concepts in a single demo or give a vague hand waving explanation of a phenomena then launch into the math. The explanation and equations will be easier to understand once the students have experienced the phenomena. C.E.g. Book & Paper (other forces), Falling beads – hearing the difference, Resonance, Electroscopes – don’t get into the sensitivity of various voltmeters (ohms/volt etc.).

#5 A.Do be entertaining & relaxed – a little showmanship can go a long way and a relaxed atmosphere will encourage the students to risk participating. B.Don’t sacrifice your dignity by being too much of a ham or allowing the classroom to degenerate into chaos. C.E.g. Hanger and String to set tone – Red Ball Express w/ breaking glass

#6 Do be inviting, enthusiastic, and encouraging – fight against the stereotype that one must be super brilliant to understand physics. Empower the students – they can do it. Don’t be intimidating, arrogant, elitist, or subordinating – My first physics course, “This is the most difficult topic you will ever study!” E.g. Scientist detector & wand - let them lead as the riddle is solved.

#7 A.Do go at a balanced pace. It is okay to have pauses for the students to think and reflect. B.Don’t go too fast or too slow – rushing does not promote learning or participation; going too slow will cause the class to drag and the students will lose interest. C.E.g. Solicit feed back from the students as a way of monitoring where they are.

#8 A.Do get the students invested in the demonstration. Make it a puzzle, a challenge or a playful deception. Make sure they thoroughly understand the experimental setup and what you are planning to do. Encourage the students to discuss the impending outcome amongst themselves. Ask them what they predict will happen - use playful betting (imaginary money), voting, or other techniques to generate friendly competition. B.Don’t enforce a silent stoic classroom; tell the students what will happen, quickly do the demonstration and then move on. C.E.g. Scientist Detector, Faster then “g”, or Racing Balls.

Modified faster than “g”

#9 A.Do discuss the outcome: Did it do what they predicted? Why/why not? What further experiments could be done to test their hypotheses? B.Don’t simply say well here is how it works and launch into a detailed numerical explanation. C.E.g. Ping pong ball and funnel etc.

#10 A.Do follow up experiments if time and equipment allows. Guide, but let the students lead the investigation. B.Don’t demean or insult their attempts. C.E.g. Series of Bernoulli demos.

Some Favorite Demos Bernoulli flat plates Scientist detector Book & Paper 2X4 and Electrostatic Rod Breaking Glass w/ Sound Young's Double Slit at Single Photon Level

The End Thank you for inviting me.