1.  DC Motors Videos
The last newsletter mentioned a UK Physics Teachers' Forum called PTNC.  A teacher, Simon Poliakoff, shared videos of a working demonstration model he had built, specifically to show the motion with and without a split ring commutator. It is an impressive video which got many appreciative responses.
In his model, the positions of the brushes are adjustable to move between the split ring setting of the commutator  and single rings setting.  In the video (7:42 min) he explains the operation of the DC motor and annotates the video with arrows for field, current and force.  He uses Fleming's Left Hand Rule.  

He also has two supplementary videos showing the motion of the coil in the single rings setting (6 sec) and in the split ring setting (1 min), The latter video clearly shows the extra push each time the coils pass the magnet. 
Some responses requested a close up of the commutator, so he produced this video.

2. Untangling a Slinky
A tangled slinky is a real challenge to undo and is often put aside and forgotten. 
This Youtube video (11 min) shows how to do it.  It is quite entertaining as well.

This website is a text-based version with images for the video.

Resource supplied by Paul Cuthbert.
  3. Radiation Dose: Tables and Calculators
The Energy from the Nucleus webpage on the Vicphysics website has a few classroom resources on radiation dose including:  Dose chart, Calculate your dose worksheet and an Online calculator.  Also check out this dosage chart from 'Information is Beautiful'.

Some other resources have been found that have useful background information and images as well.
The World Information Service on Energy (WISE) Uranium Project has several different calculators that are worth exploring:
Radiation Dose to Risk Converter. You enter a dose (a choice of units: Sv, Gy and rem), the rate and occupancy.  Click Calculate and the display gives annual dose, cumulative dose and excess lifetime cancer risk.
Uranium Decay Calculator. It covers the decay of Uranium and growth of decay products over time. You enter a value for the mass of uranium, select a uranium compound, and select chart parameters. When you click Calculate, the display gives the activity in Bq of each decay product. The useful section is further down the page which is a graph of the Activity in Bq of each decay product over 10^10 years ,.  The image to the right is an example.  It shows the sudden increase in the lighter elements after 10,000 years.
Uranium Radiation Individual Dose Calculator It covers ingestion, inhalation and external exposure. You enter a value for the mass of uranium, select a uranium compound, select the mode of exposure and the rate and click Calculate.  The display shows the dose rate in nSv/h and mSv/a.
Uranium Radiation Organ Dose Calculator. You enter a Bq value for a radioactive source, select Inhalation or Ingestion and select Calculate.  The display gives the organ dose for each of several organs as well as the contribution to the risk of cancer,

Each calculator has a Help section. The individual Dose Calculator has at the bottom of the page, links to all the other calculators.
  4. Perception of Colour and the Nature of Light
There was another interesting exchange on PTNC, see item 1 above.  This time on colour and how colour is linked to the frequency of the light and the role of the retina and the brain in determining perception.
These are some of the comments and links in the responses.

• Colour is physiological and not linked to frequency alone - you only have to consider magenta to highlight this point. As a mixture of red and blue there is no single wavelength of light that corresponds to magenta, it is entirely fabricated from the response of our cone cells.
• The photoreceptors in the eye (whether rods or cones) function by converting the energy of incoming photons into a nerve impulse. In the cones, a hydrocarbon called 11-cis retinal is combined with one of three different types of iodopsin, corresponding to R/G/B detection respectively. They are triggered by an incoming photon's energy causing a change in the positions of two of the carbon atoms in the retinal molecule, which then causes a sequence of chemical changes in the retinal, the overall effect of which is to trigger an electrical response in the nerve fibre.
• A WIRED video (12 min) on the perception of colour and the role of the brain, some intriguing images.
• The Feynman Lectures on Physics :Ch 35 on Colour Vision.

5. Events for Students

Girls in Physics Breakfast for 2024
Bookings are open and flyers are available for confirmed events.

• Traralgon, 17th May, Speaker: Natalie Clements, Medical radiation physicist, Topic: Using physics to treat cancer.
• Central Melbourne, 9th May.  AIP Women in Physics Lecturer for 2024, Prof Susan Coppersmith, UNSW, Topic: What do Theoretical Physicists do?
• Wodonga, 30th May, Speaker Dr Renee Goreham, University of Newcastle, Topic: Nanobiotechnology: Building the Future of Medicine and Beyond
• Bendigo, (Term 3).  Speaker: Dr Nadia Zatsepin, La Trobe University, Topic: Making molecular movies with X-ray lasers.
• Geelong, 15th August.  Speakers:  Prof Bre-Anne Sainsbury, Prof Wendy Timms, Deakin University, Topics: a) The Gentle Art of Breaking Stuff, b) Locking Carbon in the Ground: How, When, Where?

The cost this year is $25 per student inc GST with the first teacher free.  A discount is available.
Please check the website for more details.  Bookings can now be made for the ones with confirmed dates.  The others will open for bookings as venue and speaker details are confirmed.
 

Live-Streaming of Breakfast Talk, 8:15am, 9th May
You and your students can view the talk by the Aust Inst of Physics Women in Physics Lecturer for 2024, Prof Susan Coppersmith, on the morning of Thursday, 9th May as she speaks at the Girls in Physics Breakfast in Central Melbourne.
They are many ways for you to use the talk from the simple to the grand. These include:

1. Record the presentation and show it to the students at another time.
2. Invite students to view the presentation live and so be able to contribute questions for the speaker.
3. Offer the students a light breakfast at the school before viewing the presentation.
4. Invite people who have a career in STEM or are studying STEM subjects at university to join the students for an informal light breakfast before viewing the presentation. Your school alumni are a good source.
5. Make the event more structured by including some careers-based activities or a small panel from among your guests.
6. Contact a nearby school and make it a combined event.

Check our website for advice and suggestions for the above options as well as to register for the Zoom link. Prof Coppersmith's topic is 'From Grains of Sand to Quantum Computers'.  The website also has further information on Prof Coppersmith and her talk.

The Girls in Physics Breakfasts Program has a limit on the number of students per school to maximise the number of schools able to attend. Live-streaming enables more students to be involved.  Last year Kew High School organised their own in-house breakfast with their alumni as the principal source of guests.  It is their planning and experience of that event that is the basis of the advice on the website.

6. Events for Teachers 

a) Out-of-Field PD for Science Teachers: Forces and Motion twice, Electricity: Three events, All in-person
The next one is on Forces and Motion, it is in person and at Wangaratta on 2nd and 9th May.  The cost is $220 and there is CRT coverage for Government schools.

There is also one on Electricity, done in person in the after-school format at John Monash Science School, on Thursdays, 16th May to 20th June from 4:30pm to 6:30pm.

Then Forces and Motion will be at Leongatha on 12th and 19th June.

Check here for details for all three events.

Material is being developed for PD on Light and Sound, and Energy which are expected to be conducted in the 2nd half of the year.



b) Special Relativity: On line PD Term 2
Theo Hughes will be repeating of last year's online PD on Special Relativity in Term 2.  It will be on Thursdays, 9th May to 13th June, from 4:30pm to 6:30pm. 
The cost is $265 with discounts for Vicphysics subscribers
Check here for details.



 

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9.   Physics News from the Web
Items selected from the bulletin of the Institute of Physics (UK).
Each item below includes the introductory paragraphs and a web link to the rest of the article.
a) Peter Higgs: Nobel-prize-winning particle theorist dies aged 94
The British theoretical physicist Peter Higgs, whose work led to the discovery of the Higgs boson, died yesterday on 8 April at the age of 94. Higgs’s work, which he carried out in the early 1960s, resulted in the prediction of a new particle, setting in motion a decades-long hunt for it. The Higgs boson was finally discovered at the CERN particle-physics lab near Geneva in 2012, with Higgs going on to share half of the 2013 Nobel Prize for Physics together with the Belgium physicist François Englert.

b) New photovoltaic 2D material breaks quantum efficiency record
Convention solar cells have a maximum external quantum efficiency (EQE) of 100%: for every photon incident on the cell, they generate one photoexcited electron. In recent years, scientists have sought to improve on this by developing materials that “free up” more than one electron for every photon they absorb. A team led by physicist Chinedu Ekuma of Lehigh University in the US has now achieved this goal, producing a material with an EQE of up to 190% – nearly double that of silicon solar cells.

c) Tackling England’s physics teacher shortage with a new apprenticeship scheme
The shortage of physics teachers in England has led the government to set up a new apprenticeship scheme that it hopes will help encourage more people into the profession. But with high workloads and low pay causing many teachers to quit, Katherine Skipper asks if this latest scheme will be enough to fix the issue.

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