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  • Welcome to Spring 2024!
  • Demonstration Highlight: Inertial Reference Frame
  • Maryland Day 2023
  • Demonstrations
  • How many demonstrations?
  • New Resource: Directory of Simulations
  • New Resource: Demonstration Video Channel
  • Visit the UMD COVID-19 Dashboard
  • Physics is Phun February 2024

Welcome to the spring 2024 semester at UMD Physics! We’re looking forward to an exciting semester working with you!

If you have any questions about finding the right demonstrations or other resources for your class, access to the order form, or anything else we can help with, be sure to call or email.

Please remember to order your demonstrations before the cutoff deadline for the order form system: 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. Some demonstrations may require more notice if they use particularly complex apparatus or materials that require special handling.

It's going to be a busy spring! Our first Physics is Phun show of the year is coming up in February, more shows coming in March, and in April we will help host both Maryland Day and the the Conference for Undergraduate Underrepresented Minorities in Physics. Watch our homepage for details to come!

 

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.

Maryland Day 2023 was a fantastic success!

Visitors checking out hands-on demos at Maryland Day LN ice cream team 2023

Congrats to the whole team for a fabulous day!

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 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

 

Physics is Phun: Physics Under Pressure!

Join us Friday, February 16th, and Saturday, February 17th, at 7 PM as the UMD Physics Outreach team explores the physics of pressure.

Please register at https://forms.gle/JeBtZdMwjmKRFQms7

Physics is Phun will take place in the John S. Toll Physics Building Lecture Hall 1410.

 Physics Under Pressure Poster 2024

LecDemBlog (maintopa)

We’re paying a second visit to the Tesla Coil today, exploring more about how it works. 

tesla coil

Broadly speaking, we can wave our hands at the Tesla Coil and talk about inductance and resonance, but what does that really mean, and how does it lead to those lovely purple sparks?

Sparks on Tesla Coil

 Electromagnetic induction is the process by which a voltage is produced across an inductor in a changing magnetic field. In this case, we’re taking advantage of the studies of Maxwell and Faraday that showed the relationship between electricity and magnetism. An electrical current generates its own magnetic field; a changing electrical current thus produces a changing magnetic field, and so a changing electrical current in one conductor can induce a current in a nearby conductor. We can carefully choose these to create higher or lower induced voltages.

Electrical resonance occurs when a circuit is built to have a particular resonant frequency, at which the impedance (the way a circuit element resists an alternating current) of different components cancels out to let the circuit build up higher voltages or currents.

tesla coil circuit diagram

Our Tesla coil, circuit above, uses a 5000 volt transformer to charge a large oil capacitor. When the potential across the capacitor reaches the breakdown potential of the spark gap, breakdown across the gap occurs. The spark gap then becomes a conducting part of the RLC circuit, which resonates at a frequency of about 200 kilohertz. The large coil in the resonant circuit is the primary coil of the final transformer and the long coil of very fine wire is the secondary, producing about 200,000 volts at 200 kilohertz.

You can see what’s happening by examining a simulation of a similar circuit’s behaviour, like https://www.falstad.com/circuit/e-tesla.html . The initial transformer creates a high voltage, which eventually builds up enough to exceed the breakdown voltage of the air and make a spark across the spark gap. This then feeds into resonant circuits which build up very high electrical potential, which can create the discharge we see.

This uses Paul Falstad’s Circuit Simulator Applet, which you can explore further at https://www.falstad.com/circuit/index.html

To learn more about Tesla Coils, check out:

Nikola Tesla’s patent: https://patents.google.com/patent/US1119732

Richie Burnett’s Operation of the Tesla Coil: http://www.richieburnett.co.uk/operation.html

Wikipedia: https://en.wikipedia.org/wiki/Tesla_coil

Kelley and Dunbar, “The Tesla Coil,” American Journal of Physics 20(32). https://doi.org/10.1119/1.1933098