• Highlight of the Week: Electric Fields
  • Last Week's Highlight: Pendula of Different Masses
  • Demonstrations
  • How many demonstrations?
  • New Resource: Directory of Simulations
  • Spotlight: COVID-19 Animation and UMD Research
  • New Resource: Demonstration Video Channel
  • Spotlight: CU2MIP
  • Visit the UMD COVID-19 Dashboard

Electric fields are an important topic in physics, and one that’s particularly challenging to demonstrate clearly in the classroom. You can find several demonstrations of this in section J3 of our catalog, wherein we qualitatively trace out electric field lines around a Van de Graaff Generator or a Wimshurst Machine, and have a variety of ways of gathering electrostatic potential and showing how it interacts with conductors in different configurations. One very popular one, demonstration J3-08, uses paper streamers around one or two Van de Graaff Generators to show how the fields bend and interact.

demonstration J3-08, two Van de Graaff Generators with paper streamers

Understanding electric fields is important for everything from understanding the structure of matter to communications technology to the behavior of living cells. The electric field is a vector field of the electrostatic force (strength and direction) on a hypothetical charge placed at any given point. Thus, it is usually measured in Newtons per Coulomb or Volts per Meter.

We have an article in our Directory of Simulations with several ways of experimenting with electric fields virtually. Try out this one at oPhysics, by Tom Walsh. You can model our paired Van de Graaff Generators above as a pair of identical charges, and see the structure of the resulting electric field. Compare how this would change if one of the generators had the opposite charge, or if we used four generators instead of two.

screenshot of Electric Field simulation by Tom Walsh

 Check out other simulators as well, and see what you can find!


Welcome back! Physics PhD student Subhayan Sahu returns this week for another installment in our series highlighting oscillation demonstrations. This week’s highlight: Demonstration G1-14 Pendula With Different Masses. Check out his video below:


These swinging cubes are made of a variety of materials, from aluminum to lead. We can see that for a simple pendulum swinging under gravity, the period is dependent only on the length. So long as these pendula all have the same length, they have the same period!


You can try this for yourself in the PhET Collection’s Pendulum Lab simulation. In the lab, create two pendula with the same length and mass. Pause the simulation while you position them to the same height and release; you’ll see they have the same period. Now reduce the mass of one while keeping the mass of the other fixed; the period stays the same! Now try changing the length of one pendulum to see how that changes the period.

We’re often asked how many demonstrations we have in the collection. That’s a more complex question than it might at first seem.

At last count, we have just over 1,500 demonstrations published to the website – that is, that’s how many demonstration pages exist in the collection. But some pages describe a single setup than can be used in several different ways. Take a look at K2-61: Thomson’s Coil, for example. This single page actually describes four different, related demonstrations that can be performed with this device. They don’t require very different equipment to be delivered, just slight changes in preparation, though, and they’re usually all relevant at approximately the same point in a syllabus, so it’s simpler to list them all in one place. Conversely, there are many demonstrations that use the Optical Board – browse through section L and you will see many of them! Since ray optics is divided into several sections in the demonstrations catalog, each of the configurations of the Optical Board is listed separately, to make it easier to find the one you need; and if you’re only doing one demonstration with it, we can configure it for you in advance to save you time in class.

On the other hand, consider M1-12 and H2-22. These are both listings for Interference Transparencies, a popular way to illustrate the interaction of wavefronts. Here, we made the unusual decision to list the same demonstration twice in two different sections, since otherwise someone planning a course on sound might not think to look for relevant demonstrations in the optics section, and vice-versa. These occasional cross-references make it easier to find the demonstrations you need for your class.

And even aside from the demonstration listings as they stand, we’re often called on to combine equipment in unique ways to demonstrate something new! If it’s a combination that’s likely to be repeated or that proves useful to others, it will be added to the website, but we’re generally open to creatively reinterpreting demonstrations to fit a new class context.

Every year we add more demonstrations to the collection; and occasionally a demonstration is retired, if it no longer meets an instructional need or has been superseded by others. So defining just how many demonstrations we have might not be the right question to ask. Ask, rather, what can we demonstrate for you today?

In support of most classes moving to an online model this year, the Lecture-Demonstration staff are doing our part to help connect you to resources you need for teaching remotely. As one part of this project, we have begun compiling a Directory of Simulations from around the internet, organized by general area of physics. Find it under the Tools and Resources menu above, or click the image below.

Sample subsection titles: Electricity & Magnetism Simulations, Mathematics Simulations, Optics Simulations, Oscillations & Waves Simulations, Quantum Simulations, Thermodynamics & Statistical Mechanics Simulations

There are a tremendous number of simulations out there, that folks have been creating for years. We’re testing them out, choosing ones that we can confirm currently work (always a question as internet technology marches on) and that seem useful for our department’s classes. As of this posting, we have just over fifty simulations collected. Our initial focus has been on physics that is hard to demonstrate in the classroom, or experiments that are difficult to present as static pictures or live video.

This project is ongoing! As we continue to explore we will be adding more subjects and more demonstrations per subject. We also invite recommendations! If you have a favourite simulation, let us know (email lecdemhelp at so we can check it out and add it to the directory.

We’ll have more new projects posted soon; watch the site for news!


In our ongoing work to support remote teaching, we are pleased to announce a new resource. Over the summer of 2020, a Teaching Innovation Grant helped to create our new Demonstration Videos. These can be used for remote, hybrid, and in-person classes to present demonstrations in conjunction with class engagement questions.

The videos have their own YouTube channel, linked both here and on the Tools & Resources Menu above; check them out today!


The Conference for Undergraduate Underrepresented Minorities in Physics returns January 8-10, 2021, and we've gone virtual!

cu2mip 2020 ug flyer

Download the flyer today, and visit the website for registration and more information!

CU2MiP is co-sponsored by UMD Physics and NIST.

Science is all about data, and our current pandemic is no different. 

Be sure to check the UMD COVID-19 Dashboard for the latest campus data and links to reopening plans and  proper safety procedures.

Keep Terps Safe - UMD COVID Public Dashboard