Interacting with Multimedia in Physics Lectures
Faculty of Science Multimedia Teaching Unit and School of
Lecture theatres in many universities are commonly being set up with multimedia facilities: on-line computers, colour video projection, audio-visual facilities. How can these facilities be effectively used to enhance lectures and engage students more deeply in their learning? Does a lecturer need to learn new lecturing skills and leave behind years of lecturing habits? This paper addresses the issue of how one can use multimedia in lectures and what is required in preparation. The illustrations come from a second year electronics course for physics students.
Lecture theatres in many universities are commonly being set up with multimedia facilities: on-line computers, colour video projection, audio-visual facilities. How can these facilities be effectively used to enhance lectures and engage students more deeply in their learning? Does a lecturer need to learn new lecturing skills and leave behind years of lecturing habits?
This paper addresses the issue of how one can use multimedia in lectures and what is required in preparation. The illustrations come from a second year electronics course for physics students.
A project is underway within the School of Physics, The University of Melbourne, to develop computer-based materials to improve lecture presentations in physics. The project aims to utilise recently renovated lecture theatres to convey visually some of the more abstract and challenging concepts in physics courses.
During the past fifteen months, the University has put considerable resources into upgrading lecture theatres enabling lecturers to utilise a variety of media: computers, audio, video, slide and film projection, as well as overhead projection and black or white boards. With these upgrades in place, it is appropriate to consider ways in which one's teaching style might develop to utilise these facilities for improvement of students' learning.
The materials being developed are currently being used with students in a second year electronics subject presented in a theatre that allows you to use blackboards, overhead projections and computer screens simultaneously.
The role of these developed materials has been twofold:
* to reduce the familiar "hand waving" descriptions of how mathematical graphs behave, and replace them with simple, controllable animations;
* to present simple simulations of circuits that focus on a particular aspect of the circuits' behaviour for which students generally have trouble developing an intuitive understanding.
In addition, since the computer is present during every lecture, and does not interfere with overhead projections or blackboards, many scanned colour images can be presented to enhance the lecture's content. Not a great educational innovation, maybe, but it adds a little more interest to a lecture when a picture can be presented as an aside without interrupting the flow of the lecture.
This presentation facility also adds a touch of reality to ideas which, by themselves, convey a poor image. For example, describing a capacitor as "two long parallel plates rolled up into a cylinder" is one thing; showing a picture of a real one is entirely different!
3 Two types of presentation
This paper presents two types of presentations that have been used with students: mathematical presentations in which graphs are animated in a controlled fashion to illustrate a variable changing, and simple simulations in which particular aspects of a circuit can be highlighted.
A combination of Mathematica , QuickTime  and HyperCard  are being used for these presentations.
3.1 Using Mathematica to produce QuickTime movies
There is an abundance of software packages to enable a lecturer to plot graphs of mathematical expressions. What these packages generally don't offer is a mechanism for changing a third variable of a two-dimensional graph in a smooth, continuous fashion. One reason you might want to do this is to get a feel for how the relationship changes with that third variable. Often it would be nice to be able to grab a knob and turn it, watching the whole graph update instantaneously as you do.
3.1.1 Animating graphs
One way to produce a controllable graph is to decide which variable you wish to alter and then make a QuickTime movie from a series of graphs, each one with a different value of the variable. The result is a graph with a control bar beneath, which enables you to slide the value of the variable back and forth at will (or, if you let the movie run continuously in a looping fashion, the variable is made to change continuously in a repetitious manner).
Fig. (1) illustrates this effect. A graph is presented showing the changes that impedance and current undergo as a resonant circuit is scanned through a range of frequencies.
Figure 1. Current and impedance for a resonant circuit
The graph is a QuickTime movie. The controller beneath it allows the movie to be played (each frame in succession), or moved through, by dragging the slide bar. The different frames in this movie represent the same graph, but plotted with increasing values of the quality factor, Qo. The result is a movie that can be scanned backwards and forwards providing a good "feel" for how varying Qo affects the shapes of the graphs.
An important aspect of such diagrams is the degree of control held by the user. The graph does not simply change; it changes as the user moves the controller. This provides a very tight coupling between the user, the variable and the resulting graphical changes. This is an important ingredient in obtaining an intuitive feel for the response to a variable change. This effect is not usually achievable using a conventional plotting program. In any case, it would require a reasonably fast computer to update the graphs at the rate required for a smooth transition.
The screen represented in Fig. (2) shows a slightly different application of the same idea. Here a "vector phasor diagram" has been constructed and is made to rotate in order to illustrate phase relations between different voltages in a circuit, the projection of the x-axis being an important feature for students to focus on.
Figure 2. Phasor diagram for an RLC circuit
The range of presentations that can be constructed this way is limited only by the facilities that Mathematica provides.
Mathematica makes the construction of such movies straightforward. The mathematical expression to be plotted is placed into a program loop which changes the variable in a regular way. Each time around the loop, the program will construct one graph for the particular value of that variable.
When all is done, Mathematica can join the set of graphs together into a QuickTime movie which can then be compressed and made ready to be presented in a lecture on its own, or as part of a HyperCard (Macintosh) or ToolBook  (PC) presentation.
The time taken to do all this depends on the speed of the computer, the complexity of the graph and the number of movie frames required. However, a typical movie of 30 frames (i.e. changing a variable through 30 different values) might take about 15 minutes in total to produce. The resulting file might be about 50 kilobytes in size.
In many areas of physics there are excellent simulations allowing the exploration of a well defined domain of knowledge. Whereas these can be well used in lectures, they have two drawbacks:
* licensing arrangements for commercial packages often forbid distributing the software to students for them to run at home, in their own time;
* the simulations are often too complex. The lecturer might want to focus on only one particular aspect of the simulation, and be able to display outputs that relate specifically to that aspect.
A solution to these drawbacks is to produce simple simulations to illustrate the particular points for your lecture. Writing a simulation program just for one or two lectures might appear to be a daunting task. However, software environments such as HyperCard and ToolBook make this quite manageable, remembering that the result is not intended to be an accurate, student-proofed simulation for general use.
Producing a presentation using either of these two environments also offers the advantage of being able to arrange the simulation, together with movies of graphical functions, still-pictures and video, into a sequence ready for lecture presentation.
Fig. (3) shows a screen image from a simple simulation which uses bar graphs to illustrate the voltage and the power dissipation in different parts of a circuit. The "sliders" on the left and right of the screen allow the values of resistors to be varied, thus causing the bar graphs to change according to voltage and power at various places in the circuit.
Figure 3. Circuit simulation
Although the simulation presents only elementary concepts in circuit analysis, very few students were able to predict correctly what would happen to the power dissipated at the output of the circuit as the output resistance was increased from the value shown. The ensuing discussion was vigorous!
The software can be handed to students after the lecture, or they can collect it from the network, so that they may explore it more fully at a later time.
There are a number of commercial publishers that now produce resources which can be used to enhance lectures. Two are briefly described below.
Some text book publishers are producing software to accompany their texts which enable lecturers to present animated diagram on screen to a lecture group. One such publisher is Wiley who produce a bundle of software to accompany the first year physics text Fundamental Physics . Some of this software is an attempt to assist students in problem solving and is, in this opinion of this author, lacking in many respects.
However, Wiley also distribute a set of discs  which contains about 50 animated diagrams from the text. The quality of these diagrams is excellent. They are essentially movies constructed in MacroMind Director  which are played via a menu screen. Some of them run two or three times with different values of variables.
However, generally the lack of user control does not let these animations offer their full potential. One cannot play the animations backwards and forwards, slowing down at crucial points in order to examine an interaction closely.
Fig. (4) shows one of these diagrams in which a cannon is fired inside a railway truck illustrating conservation of momentum.
Figure 4. Example from a commercial package
Another commercial product being utilised by text book publishers is Interactive Physics . This is a physics simulation environment allowing the user to construct objects in a Newtonian world (in a free form drawing environment) and then let the simulation run and observe the ensuing outcome. It is an extremely powerful product offering a range of variables (such as mass, elasticity, friction, electric and magnetic fields, charge, air resistance) and a range of objects (such as polygons, springs, pulleys, motors, actuators, levers, strings, joints) and the display of expected quantities (such as kinematics vectors, force vectors, energies, graphs, and so on).
Interactive Physics is an excellent simulation and problem-solving environment in its own right. Several text publishers, however, have used this environment to set up some of the problems from their texts so that students can explore the problem as they attempt to solve it (for example: Giancoli , Fishbane ). A "player" application is supplied with these problem sets that allows a set simulation to be played, but not to be edited.
This not only provides support for students in solving the problem, but also encourages students to explore "what if" type questions relating to the problem after they have completed it.
Whilst these simulations can be displayed in lectures, they require a fast computer (Macintosh or Windows) to run a complex simulation in reasonable time. However, if a prepared simulation, with a predetermined set of parameter values, is to be displayed, the simulation output can be saved as a QuickTime movie and displayed in a fast, smooth fashion. This offers the ability to stop, go forwards and backwards and retain good control.
If multimedia presentations of the type described above are to be used in lectures, then we need to consider what is required for their production as well as what is required within the lecture theatre to enable them to be used effectively.
One approach to setting up multimedia material for use in lectures is to employ a commercial presentation package such as PowerPoint . Packages like this one enable you to construct high quality, colourful displays incorporating pictures, diagrams and QuickTime movies. There are, however, limitations to this kind of presentation.
One limitation is that QuickTime movies imbedded in PowerPoint are not, at present, controllable--other than to start them playing. This removes much of the value of being able to "drag" through them forwards, backwards, slowly and quickly.
Another limitation is the lack of programmability. Whilst the screen can be made to build up nicely, one heading after the other, there is little other animation or calculation that can be employed on-screen. Some applications can be launched from within a screen, but these are very few at present.
If this type of package is to be used for a complete lecture presentation, then, of course, it has the advantage of a very clear presentation of text and diagrams, as well as the ability for students to obtain printed copies from a network to supplement their own notes. However, such an "all electronic" presentation removes much of the dynamic aspect of lecturing: scribbling comments, numbers and freehand sketches to an overhead transparency; jumping around a large diagram on a blackboard; constructing and deconstructing diagrams and workings during problem solving.
There needs to be a careful evaluation made here of a precise, clear presentation on the one hand and a more dynamic, lively presenter on the other. The two need not be exclusive.
Scripting environments, such as HyperCard (Macintosh) and ToolBook (PC) enable you to construct a sequence of screens for a lecture, each containing text fields, buttons, diagrams and animations. Since these environments support programming scripts, you can also produce simulations, carry out calculations and have full control over QuickTime movies.
Greater expertise is required to use such environments, but once a template is set up, the production of a series of screens for a lecture is quite straightforward. They have the advantage of enabling other programs, such as simulations, to be launched from within them such that when you quit, you are returned to your lecture series and can carry on with the sequence.
All of the software mentioned so far runs satisfactorily on mid-range machines (eg. Macintosh LC III and 80486 PC). However, for the production of the various multimedia components, a faster machine is highly desirable.
Moving electronic colour images taxes computers heavily due to the immense data sizes involved. Hence, for development, a computer with fast graphics is advisable as well as plenty of RAM.
Digital movies, whether they be animations, graphs or video, can occupy vast amounts of hard disc space. Data compression will reduce this significantly.
If videos are to be displayed, or still photos, then appropriate hardware will need to be on hand to capture the images before compressing them to disc. This means a digital frame-grabber for videos and flatbed or slide scanner for photos.
The design of lecture theatres equipped for multimedia use will have a great influence on whether lecturers take up the challenge to use them, or not. At The University of Melbourne there are a variety of designs currently in use. Some encourage an all-electronic lecture while others allow greater mixing of the media.
Many of the University's upgraded lecture theatres have a central whiteboard which can be covered by a computer projection screen, lowered electrically. Due to the time it takes for the screen to lower, this dictates that whiteboards (or blackboards in some theatres) cannot be used interchangeably with computer displays
This makes it difficult to interleave a computer presentation with a more traditional whiteboard presentation as one has to compact all the computing into one or two chunks of time to avoid time-wasting screen lowering. This is a disincentive for lecturers to take up the use of this technology as it means significantly changing the way in which they teach: it is awkward to "try a little bit" and see how it goes. The alternative is, or course, to present the whole lecture electronically--even more threatening!
One lecture theatre in the School of Physics has installed a video and computer projection facility, together with video player.
Although not as extensive as upgrades in many other theatres this particular upgrade offers something that the others don't: the screen is located in the corner of the theatre, rather than overlaying the blackboards or overhead transparency screen in the centre of the front wall. This might appear to be a trivial point, but it is significant in the possibilities that the theatre now offers.
For a lecturer who makes significant use of blackboards or overhead displays during a lecture, those facilities are still there and can still be used in the traditional manner. The projection screen is now also available to be used in addition to the other boards.
For example, a computer can be employed to display the objectives of the lecture, graphical images, simulations and animations. The value of this is not just that it can be done (it always was possible), but that it is now very easy, requiring little special setting-up. The lecturer can go back and forth from overhead to computer during a lecture without having to lower screens, move chalk boards or switch on slide projectors.
The images presented remain visible as the lecturer continues with the more traditional presentation.
The new system has had a positive effect on interaction in that it has encouraged much more lecturer-student dialogue. For example, simple situations have been presented to students for them to make predictions along the lines of "what would happen if... ?".
These "on-the-side" presentations break the monotony of staring at a overhead display and have prompted many more students to actually think and vocalise in lectures!
It is not sufficient to introduce the kinds of presentations discussed above without giving thought to a rationale for their adoption. This can be viewed from the perspective of our teaching and from that of the students' learning.
With the facilities in place, and, unfortunately, with some additional input of time, we have no excuse for not making use of these facilities if we believe it will be of value to students. It is worthwhile keeping your eyes open for the appropriate photo, or photo opportunity, that might embellish a lecture; for that animated graph that might reduce the hand-waving or that piece of software that might convey the concepts that you are trying to develop.
The real challenge, is to try to engage students more effectively in their learning within a lecture setting. If we display a pretty picture, then we have done no more than that--motivating at best.
However, if we can present something on-screen which we require students to think about, make a prediction about and then watch and explain the outcome, we stand a good chance of engaging their minds actively rather than them passively copying down notes.
In a small lecture group this will cause increased discussion. This is good and highly desirable for students' learning. However, it will mean rethinking the content of lectures as not so much will be covered in a set time. This is not a negative point, as we so often confuse "my coverage of content in a lecture" with "student's learning of content in a lecture." Very different things!
In larger lecture settings, it might not be possible to engage students in an active dialogue. However, they can be asked to predict to themselves, or to the person next to them, the outcome of a demonstration. The mere fact that they think before they are shown, improves the chance of them grappling with the concept being presented.
In all cases, it is highly desirable if students are given the opportunity to take home copies of the presentations shown in lectures. The most value will be gained when they are able to play with the interactions for themselves.
Experience so far this year shows that the use of such "cameo" pieces in lectures are very well received by students and help to develop more interaction and activity during the lectures. The extent of effort required for their production is more akin to lecture preparation than software development, although this still represents a considerable amount of time.
These applications of multimedia to lecture presentations are highly interactive and stimulating and offer various ways in which these media can help us to change and improve our teaching efforts.
 WOLFRAM RESEARCH, INC., Mathematica, Champaign, 1988.
 APPLE COMPUTER INC, QuickTime, Cupertino, 1989.
 APPLE COMPUTER INC, HyperCard, Cupertino, 1989.
 ASYMETRIX CORPORATION, ToolBook, Bellevue, 1992.
 HALLIDAY, D, R RESNICK and J WALKER, Fundamentals of Physics, Wiley, 1993.
 CHRISTMAN, J and S MADDOCK, Interactive diagrams to accompany Fundamentals of Physics, Wiley, 1993.
 MACROMIND INC, MacroMind Director, San Francisco, 1993.
 KNOWLEDGE REVOLUTION, Interactive Physics, San Francisco, 1992.
 GIANCOLI, D, Physics; Principles with Applications, Prentice-Hall, 1991.
 FISHBANE, P, Physics for Scientists and Engineers, Prentice-Hall, 1993.
 MICROSOFT CORPORATION, PowerPoint, USA, 1992.
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