## Interactive Lecture Demonstrations

Beginning in the fall semester of 1999, the demo room will have several Interactive Lecture Demonstrations (ILDs) available for use in the classroom. Ron Thornton at Tufts University, the director of the Center for Science and Mathematics Teaching (CSMT) , and David Sokoloff of the University of Oregon have co-developed a set of ILDs, and we will adapt and develop our demonstrations from those. Prof. Thornton has also agreed to act as a consultant on this, and his experience and expertise should be invaluable to us.

A typical ILD is structured as follows:

1. Professor describes the experiment, and carries it out without recording data.
2. Students record their predictions of the outcome on a Prediction Sheet.
3. Peer discussion follows, with the students discussing their predictions in small groups.
4. Professor engages class, soliciting predictions and highlighting common predictions.
5. Students record their final prediction on the Prediction Sheet (this is collected).
6. The experiment is run. Real data is recorded and plotted by the computer, with the results displayed graphically for all to see.
7. Professor engages class, discussing what students say about their predictions and focusing in particular on any common misconceptions. Students record the results on a Results Sheet, which they keep.
8. Professor discusses variations of the experiment and similar physical situations based on the same underlying concepts.

The ILD process is quite involved, and is generally used in just several classes each semester. Even that level is enough to produce substantial benefits, according to recent studies. In the following reference, for instance,

D.R. Sokoloff and R.K. Thornton, "Using Interactive Lecture Demonstrations to Create an Active Learning Environment", Phys. Teacher, 35, 340 (1997).

the authors compare student understanding of dynamics in a traditional course compared with a course with four ILDs. In a typical case, 10% of the students understand the concept before instruction. This rises to about 20% after instruction in a traditional lecture course, compared with at least 80% in a course involving ILDs.

A good example of an ILD we are planning to implement is the measurement of g, the acceleration due to gravity. Our standard demonstration involves timing a ball as it falls through a known distance. The drawback here is that the students can read neither the ruler nor the timer for themselves. In contrast, a computer can display graphs of the position versus time, and velocity versus time, for all to see. The lineraity of the velocity graph demonstrates that the acceleration is constant, and with a click of a key the computer can get the slope of the velocity graph, giving the acceleration. The process should be much more satisfying for both the students and the instructor, and increases student understanding far beyond the level reached with traditional methods.

For each ILD, I will put together a student prediction sheet. This could include graphs where the students could fill in their predictions of the shape of the curves, as well as a few conceptual questions. You can use that or adapt it to suit your purpose (feel free to pass along any ideas for improving these handouts). The ILDs being developed this summer (1999) include:

• measurement of g - freefall with motion recorded by a photogate
• constant acceleration - motion of dynamics cart on an inclined track
• friction - cart on an inclined track with variable friction
• collisions - the forces involved in elastic and inelastic collisions
• simple harmonic motion - a simple pendulum
• radiation - cooling curves for a black can and a shiny can to show which cools at a faster rate
• heat engine - a cycle on a P-V graph
• Ohm's law - voltage vs. current for ohmic and non-ohmic devices
• RC circuits - current and voltage as a capacitor charges/discharges
• induction - emf induced in a coil by a magnet
• polarized light - intensity of light after passing through two (or three) polarizers

If you have ideas for others please let me know.

### What you can do

If you would like to participate in the development of the ILDs, perhaps by coming up with new ideas or designing the handouts for the students, I would appreciate your assistance. If you'd just like more information, or would like to see a demonstration of an ILD, contact me, too. The best way to reach me is by e-mail at duffy@buphy.bu.edu.

- Andrew Duffy

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