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  • Welcome to Spring 2025!
  • Demo Highlight: Convection With High & Low Candles
  • Demonstration Highlight: Inertial Reference Frame
  • Demo Highlight: Ring and Disc on Inclined Plane
  • Demonstrations
  • New Resource: Directory of Simulations
  • New Resource: Demonstration Video Channel
  • Visit the UMD COVID-19 Dashboard

Welcome to 2025! We at the Lecture Demonstration Facility are looking forward to working with you in the spring semester.

We appreciate as much advance notice of demonstrations as you can give; but at a minimum, please remember to order your demonstrations before the order cutoff deadline: For morning classes, before 1PM the previous working day; for afternoon classes, before 4AM the day of the class. Where possible, we appreciate having the orders at least one full working day ahead, to ensure plenty of time to make sure everything is ready for you. As always, we’ll meet with you before your class to go over the demos and make sure everything is ready to be used effectively and safely.

Here's to a great semester!

The behaviour of gases as they're heated and cooled can be confusing, but is really important to understanding a lot of things in daily life, from the weather outside to heating a house to designing power plants... or simply to how candles burn. Demonstration I2-45: High & Low Candles in a Cylinder gives us an example of this.

 I2-45: Two small candles burn inside a clear plastic cylinder. One sits at table height, the other is elevated on a slim metal pedestal.

Read more on the Physics LecDem Blog!

 

 

Welcome back! Today we’re taking a look at a popular demonstration related to the concept of relativity.

 When we observe and measure motion, we are inevitably making the measurement against some frame of reference. An inertial reference frame is the technical term for a frame of reference in which an object is observed to have no outside forces acting on it, so that it is moving freely in space. Sometimes we have to go to great lengths to determine what such a frame of reference might be – and in the case of Demonstration P1-02, it is literally a metal frame!

 Demonstration P1-02: The Inertial Reference Frame, a large aluminum framework with a mounted winch to lift it.

Read more about this exciting demonstration and how it can be used in class in our latest blog post.

In recent years, the classic term “moment of inertia” has started to be largely retired in favor of the more descriptive “rotational inertia;” likely a good choice, as “moment” has long since ceased to have any non-time-related usage in everyday English. But call it what you will, it can be a challenging concept for beginning students to wrap their heads around.

Demonstration D2-01: Ring and Disc on Inclined Plane is a useful illustration for clarifying this concept. Two objects of similar mass and radius, a metal ring and a solid wooden disc, are placed on an inclined plane with no initial velocity. As they are accelerated by gravity, the disc quickly outpaces the ring. You can invite students to make a prediction ahead of time about their behaviour, presenting it as a race between the two objects, and invite them to discuss the results afterwards.

A wooden disc and a metal ring sit on a table next to a wooden ramp

Read more on our blog!

 

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 physics.umd.edu) 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!

demovideospreviewmatrix1

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!

 

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

 

LecDemBlog (maintopa)

Demonstration J4-51: The Theremin is a fun and exciting way to illustrate electrical capacitance. You can see it in action in this new video with Angel Torres.

The theremin is an electronic musical instrument invented in the early 20th century by Russian scientist, engineer, and cellist Leon Theremin. As well as his musical work, Leon Theremin developed many other electronic devices in his career as an engineer, including an early motion detector and listening devices for espionage.

The two metal “antennas” on the sides of the theremin are not antennas in the usual sense. Each one functions as one plate of a capacitor. When you move your hand near the antenna, your hand serves as the other plate of that capacitor. Thus, each functions as a variable capacitor, where the capacitance, the ability of this air-filled capacitor to store electrical charge, varies as you move your hand and body near the antenna.

Each of these capacitors is part of a variable RLC (resistor-inductor-capacitor) oscillator circuit. One of these variable oscillators controls a second internal oscillator circuit; these together create the output frequency (or pitch) of the sound from the theremin.

The other variable oscillator, meanwhile controls the output amplitude. The resulting signal is fed through an amplifier circuit to a speaker. Together they form an electronic system that can create music, controlled by the motions of your body – without the player ever actually touching the device.

The theremin has been used in a wide range of music. Much of the early technique of playing it was developed by classical violinist and thereminist Clara Rockmore. The theremin can be heard in the work of orchestral composers like Dmitri Shostakovich and Percy Grainger, and in rock bands including the Rolling Stones and Led Zeppelin. And you can hear it on the sound tracks of movies ranging from Cecil B. deMille’s The Ten Commandments, to the science fiction classic The Day the Earth Stood Still, to the 2006 animated film Monster House.  It’s a beautiful way to see and hear the fusion of art and science.

 J4-51 Theremin; with stand, amplifier, and speaker

Our theremin seen here was built by the Moog Corporation, best known for their electronic synthesizers.

 

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