Month: April 2010

Leaving Cert Physics: Derivations

There are a total of 11 derivations on the Leaving Cert Physics syllabus:

1. Three equations of motion

2. F = ma

3. v = r w

4. Relationship between Periodic Time and Radius for a Satellite in Orbit

5. To show that any object that obeys Hooke’s Law will also execute SHM

6. Equation for a diffraction grating

7. Resistors in series and in parallel

8. F = Bqv

I have put the derivations together in a single word document, together with the year in which they have appeared on an exam paper.

It can be found on the revision page of thephysicsteacher.ie

Hope it proves useful

Let’s remove voltage from the Junior Science syllabus; post #1

 

Dear Mr/Ms Junior Cert Syllabus writer,

The time has come to question why the concept of voltage is still on the Junior Cert syllabus.
It is by far the most difficult concept for students (and indeed teachers) to grasp.
Consider a relevant extract from the Junior Cert Science syllabus

Set up a simple electric circuit, use appropriate instruments to measure current, potential difference (voltage) and resistance, and establish the relationship between them

Let’s take a look at potential difference (commonly referred to as ‘voltage’):

The following extract has been taken from the minutes of a History of Science meeting, in 2002.

John Roche, of Linacre College, Oxford, opened the session after tea, speaking on the concept of voltage. He began by claiming that almost every concept in electricity and electromagnetism is ambiguous, and the concept of voltage is one of the most incoherent. Its evolution is difficult to follow.

 Abbé Nollet, in the 18th century, distinguished quantity and degree of electrification. Others made similar distinctions between quantity and intensity or tension or pressure – what we would call voltage.

 Roche showed how the term “voltage” had come to be used nowadays in three different ways; for electromotive force, potential difference and (absolute) potential.

Volta defined electrical tension as the endeavour of the electrical fluid to escape from a body. Volta’s tension was more akin to a force, unlike the modern definition of electromotive force, which is a misnomer, being defined in terms of energy.

Ohm carried Volta’s concept to closed circuits with the idea that voltage was proportional to the difference in tension between the ends of a conductor. For Ohm, it was the gradient of electrical tension that drove the current.

Poisson introduced an entirely different concept, of charge divided by distance to a point, which Green called the potential. This was an analytical device only, arising from an analogy with Laplace’s gravitational potential function.

Kirchhoff reconciled Volta’s tension with Poisson’s potential function through the concept of energy or vis viva introduced by Helmholtz. From Kirchhoff, current is driven by the electric field in a conductor and voltage is related to the energy supplied, but physicists and electrical engineers do not usually think of them in this way.

All the earlier interpretations remain current, but with different weights, and most of the time voltage is seen as a driving energy.

 IOP History of Physics Group Newsletter, Spring 2000, page 65

So what exactly should we be telling our students about potential difference? How many (non-physicist) science teachers can define or explain potential difference? Maybe most can, but if so I would be very pleasantly surprised.

Would it hurt anyone if we replaced the syllabus extract above with something more simple, like the following?

Set up a simple electric circuit using appropriate instruments to light a number of bulbs in series.
Understand that for current to flow a power supply and a complete circuit are required.

The other aspects of the syllabus on electricity could remain as they are, but no Ohm’s Law, no experiment to verify Ohm’s Law, no mathematical problems based on Ohm’s Law, and no more mention of potential difference.

Leaving Cert Physics: Definitions from Past Papers

This word document has now been updated; not only does it now include all definitions from the 2009 paper but it also includes all definitions from Ordinary Level papers from 2002 – 2009.
The document can be accessed from the revision page of thephyiscsteacher.ie

The answer to each question is also included; hopefully this allows for non-physics friends/parents/brothers/sisters to ask the questions and check the answers as you go along.

It is notable that in some instances the ordinary level definitions are actually more difficult ( and at times rather obtuse) than the higher level questions. I have noticed something similar in the Junior Cert Science papers over the years. I suspect that while many of us write in to exams commission to comment on the higher level paper, few of us ever bother to analyse the ordinary level paper in the same detail and so these anomalies go unchecked.
Anyways, as always the document is on the leaving cert physics revision page.
Hope it’s useful.

Pseudoscience

Astrology, telekenesis, ESP, telepathy, clairvoyance, telling the gender of an un-born baby by the spin of a pendulum and of course dowsing. What do they all have in common?
Answer – they are all examples of pseudoscience.

The Iraqi government has spent over $85 million on an electronic dowsing machine. Given that dowsing is one of those phenomena situated comfortably in the middle of the pseudoscience spectrum it is difficult to know why people seem so surprised that it doesn’t work. I suppose having a name like “ADE651” does make it more impressive. Still . . .

Pseudoscience is one of the topics we look at in our Transition Year module entitled Ten Great Ideas. Links to other resources are here.

For a wonderful introduction to pseudoscience see Michael Shermer’s presentation at TED entitled ‘Why people believe weird things’.

Erupting volcanoes – resources for teaching

The CESI forum has been wonderful this week, providing a series of links for up to the minute news on the Eyjafjallajokull volcano which erupted this earlier in the week.

I hope they don’t mind if I borrow their links.

NASA Photo

Helicopter footage of the erupting volcano

Beautiful Photos of the eruption

Watch flights over Europe – live!
This site seems to be down at the moment – I’m not surprised.

Visit here, select [24] frames, and press [Play] … you can see the color radar starting yesterday and then the actual effects of the eruption.

Two videos from Sky News
1: Background to the eruption
2: Pilot tells his story of flying into an ash cloud

And finally a wonderful blog post (with a National Geographic video embedded) from a fantastic school blog – thank you to msleydonsclassblog – and thanks to the Teachnet gang for pointing to it in their most recent post.

But most of all thanks to the good folk at CESI who continue to demonstrate the power of collaborative learning. Chances are, most of you reading this are signed up anyway, but if not why not do so now? Just go to their homepage and down at the bottom you will see the option to subscribe – you won’t regret it (but if you do you can always unsubscribe at any stage).

And never forget children: Nature – it always bites you in the ass.

Junior Cert Science – a guide to answering Maths questions

Answering maths questions is a skill which intimidates many students at Junior Cert level.
the revsion page of thephysicsteacher.ie now offers a guide to answering maths questions in the exam. It includes a full set of maths questions and solutions taken from past-papers at higher and ordinary level.

Hopefully seeing it laid out in this fashion will encourage students to see (i) the importance of learning the formulae, and (ii) how straightforward the questions actually are once the formulae are known. There is a general belief that all formulae are in the new log-tables and that therefore nothing needs to be learnt off, whereas in fact only half of the formulae are there. The revision-guide includes a reference to these and where to find them. It also includes a set of practice questions.

No password required etc. Hope someone finds them useful. As always all I ask is that you follow the suggestion on the top of the first page in relation to saving paper.

Junior Cert Science – a guide to answering exam questions

The ability to draw and interpret graphs is a skill which gets tested every year in the Junior Cert exam.
However I have yet to see a lesson-plan on this;  usually each graph is dealt with separately in its corresponding chapter. Which is why the revsion page of thephysicsteacher.ie now offers a guide to answering graph questions in the exam. It includes a  full set of graph questions taken from past-papers at higher and ordinary level.

Each graph is explained and solutions provided, including an emphasis on the importance of knowing the formula for calculating the slope, the significance of a line going through all data points and the origin, and the trick to drawing a ‘best-fit’ line (this is not on the syllabus but is only one more example of something not on the syllabus coming up on the exam paper).

There is no password required to access the resource, no log-in process, no funny handshake, no ‘you show me yours and I’ll show you mine’. As always, feel free to take it, adjust it and make it your own – life is too short to do otherwise. Make no mistake – this will be very useful to most students. All I ask is that you follow the suggestion on the top of the first page and photocopy A3 – A4 (this puts two pages onto one) and then use front and back of the page  to save paper.

There are a couple of other resources on the revision page and one or two more which should be completed and uploaded in the near future – stay tuned.

Physics, Hollywood and Rock Stars

What Hollywood actress said the following in a recent interview for GQ magazine?

I’m interested in elementary particles, any spare time I have, I bury my head in a physics textbook. The elements at the atomic and subatomic level make up everything. You, me, the buildings, our souls, our minds. I’m reading a lot about Einstein. I like theories. I want to understand string theory. I’m dying for someone to explain quarks to me!

Answer
Anne Hathaway.

What rock-star recently acknowledged that watching quantum physics videos on YouTube had affected her music?

Quantum physics has done my band a world of good.

Answer
Courtney Love

Thanks to Physics World for those.
It reminds me of the beginning of the brilliant E = mc squared; A biography of the world’s most famous equation, written by David Bodanis, where the author describes his inspiration for writing the book:

A while ago I was reading an interview with the actress Cameron Diaz in a movie magazine. At the end the interviewer asked her if there was anything she wanted to know, and she said she’d like to know what E = mc squared really means. They both laughed, then Diaz mumbled that she’d meant it, and then the interview ended.

All the material required to make Leaving Cert Physics a fascinating subject already exists – all we have to do is bring it together.
Don’t hold your breath.

On the lack of wonder in education: Monbiot hits it on the button

George Monbiot, who writes for The Guardian, finished a recent piece on communication in science with the following:

We are deprived by our stupid schooling system of most of the wonders of the world, of the skills and knowledge required to navigate it, above all of the ability to understand each other. Our narrow, antiquated education is forcing us apart like the characters in a Francis Bacon painting, each locked in our boxes, unable to communicate.

There’s that word again: wonder. Why does eveybody ignore this- surely it’s not that difficult to fix?

Survey finds Physics dropped in 10% of schools

With all the media attention on NAMA these times it’s understandable that most of us missed this headline from RTE the other day (hat-tip to eagle-eyed Jude for bringing it to my attention).
The RTE article leads with the following:

Research suggests that almost 10% of second level schools have been forced to drop Physics as a subject offered to students.
The findings indicate that the decision is as a direct result of education cutbacks.

Not a happy statistic, but presumably many of these schools had less than ten students in the class, and it just wasn’t feasable to maintain this. So why don’t more students do physics? It’s a very complex issue but the problem is causing concern to authorities throughout the western world. I believe that one very important factor is the picture of physics which students get from the  Junior Cert – if we don’t get this right then it’s going to create a poor impression when they go to choose their leaving cert subjects.

So what would I change in Junior Cert Physics? – stay tuned.

btw – should we read anything into the fact that the accompanying picture in the RTE webpage is chemistry-related, not physics?