Unusual resource for explaining Joule’s Law

An offshoot of Joules’ Law is that when transmitting electrical power, the current is kept as low as  possible in order to reduce energy losses associated with heat of the electrical cables. Because the power being transferred is the product of the voltage and the current, we can still get the same power transferred if we halve the current and double the voltage, or; make the current very, very small and make the voltage very, very big.

So power -lines transmit power at a voltage of up to 400,000 volts. Then, as the power gets closer to the home, the voltage is reduced in stages, and correspondingly the current gets increased. This occurs in appiances called transformers.

I came across a lovely interactive explanation of this when in honeymoon in Hong Kong.
I couldn’t resist.

Mr Devitt teaches us about Light

Jerome Devitt (History Teacher) runs a transition-year module on Light and Sound for theatres, and kindly agreed to allow us in to watch him teach one of his lessons.

Not all of it comes out great on video, but it should still prove very usefull for Senior Phyics classes.

If you would like to play with a virtual version of this, where you can control the postion and intensity of the lights, click here.

Thanks Jerome

The old bed of nails

We have Open Day coming up and I was considering using the bed of nails. It’s certainly impressive, but I think we may not have enough room or time on the day.

It’s pretty cool though. And the nice thing about it is that the more nails you have on it per unit area, the more dangerous it looks but the safer it actually is (from Pressure = Force / Area).

Then all you need to add is another bed on top, and on top of this a cavity block.

Then smash the block with a sledge-hammer (this to demonstrate the property of inertia).

Then add more beds!

More teaching ideas from teachers tv

My friend Dee Maguire reminded me recently of some very useful videos on teachers tv of physics teacher David Robinson in action. Some of these are also on youtube:

The magnetic gun is also referred to as a ‘Gaussian gun’.
We had a bit of fun puting a basic one together at the end of class the other day.



Other video clips of David demonstrating can be found here on teachers tv; the radioactivity clip is particularly impressive.

You can also enter his name into the youtube seachbox for other demonstrations.

Thanks Dee

Questioning Science Education

Starting with four basic questions (that you may be surprised to find you can’t answer), Jonathan Drori looks at the gaps in our knowledge — and specifically, what we don’t know about science that we might think we do.


So goes the blurb for the one of the latest talks on TED.  Drori asks four basic questions:
1. Where does the “stuff” in trees come from?
2. Can you light a torch bulb with a bulb, battery and a single piece of wire?
3. Why is it hotter in Summer than in Winter?
4. What is the shape of the planets’ orbits?

How many can you answer correctly?

Drori then refers to a couple of videos he was involved in producing a few years ago where graduates of MIT were recorded giving their answers to some of these questions, and surprise surprise, almost all were unable to answer any question correctly. There is a nice moment when one young woman, on finding that she is incapable of puting the electric circuit together, justifies her lack of knowledge by saying “I’m not an electrical engineer, I’m a mechanical engineer”.
Drori wasn’t able to use the clips in his presentation due to a technical hiccup, but I am assuming that these are the videos he is referring to. The first is entitled “Can we believe our eyes?”, while the second is “Lessons from thin air”.

I referred to these videos in a post last year, and mentioned that the answers given by graduates were very similar to those given by six year olds. What I didn’t realise is that, according to Drori, research shows that concepts like Magnetism and Gravity are better understood by children before they go to school than afterwards!

This is stunning, and a little difficult to believe. I would like to find out where he got his information here, but then again, just because it goes against common sense isn’t reason enough to disregard it.

Another question asked in the “Can we believe our eyes?” video goes something like this;
Imagine you are facing a mirror. If you want to see more of your body should you move towards the mirror, away from the mirror, or does it not make any difference?
The point being made here is that ‘hands-on’ experience is not necessarily very educational. They even received incorrect answers from the barbers who work with mirrors every day. It reminded me of the recent fascinating discovery that cattle and wild deer tend to align their bodies in a North-South direction when standing in a field (link). How could we not have noticed that before?

I guess if we are not directly interested in something (almost at an emotional level) then we are rather unlikely to notice or form a deep understanding of it, and the traditional teaching approach of simply repeating the class lesson is of little use in changing that.

I know myself that I learned bugger-all physics in six years of secondary school or four years of college. I did however learn more in one year of teaching Leaving Cert Physics than I did in all the others combined. This was obviously because I was no longer ‘learning’ to pass an exam, but rather I was learning to survive in a classroom where I knew  I would be taking questions from students who were expecting nothing less than an A1 in their Leaving Cert. I had taught in a previous school but had spent too many lessons ‘winging it’ and getting caught out, so for me this was a fresh start and therefore there was certainly an emotional motivation.

Which is why, if I find out that my students know less about magnetism and gravity now than they did before I taught them, I may just have to find a cold, dark room and lock myself in it for a long time.

Particle Physics and the LHC: some useful resources

The Large Hardon Collider is due to be turned on this day next week (Wednesday, 10th of September), so it’s not a bad time to put together some useful resources to show to the troops to give them some idea of what it’s all about.

At just under 5 minutes, the Large Hadron Rap isn’t a bad place to start:

The ‘rappers’ mention dark energy and dark matter; comprising 96% of the universe between them, they can’t be directly measured, but their influence is immense. Find out more by watching Patricia Burchat speak at TED:

Want more? Try ‘Most of the Universe is Missing

Mary Mulvihill over at Science@Culture reminds us that BBCRadio 4 is devoting the entire day to the event. Watch Dara O’Briain, among others, give his rather unique take on the event. Not a big fan of homeopathy or Deepak Chopra is our Dara. He does appear to be a fan of Physics though; ‘wonder how he got on with Science in school? He strikes me as someone I’d have to keep on when it came to handing out chemicals!


This link is to the CERN website.

Over on Teacher’s TV you can watch Brian Cox present ‘In Search of Giants’; three 15 minute programs:

The Building Blocks of Matter

The Hunt for the Higgs

The Forces of Nature

Finally for teachers, there are various free resources, including posters, available here.

The Periodic Table of Videos

Tables charting the chemical elements have been around since the 19th century – but this modern version has a short video about each one.

In the short time since launching this site, our videos have been watched more than 1.8 million times.

But we’re not finished yet. We’ve started updating all the videos with new stories, better samples and bigger experiments.

So once you’ve watched all 118 videos, make sure you come back and check on our progress. We still have a few surprises up our sleeves!

The video above is a short introduction. Find out more at

Excellent resource; thanks Ewan.