James Clerk Maxwell and the Second Great Unification in Physics


James Clerk Maxwell

Newton unified physics and astronomy: this was the first great unification in physics. Maxwell unified electricity and magnetism – the second great unification.  James Clerk Maxwell should be as well known as Newton. Newton has his three laws. Maxwell has four equations. We can understand Newton’s laws at high school, but we have to wait until we have studied enough mathematics to understand Maxwell’s equations. That’s why he is not well known – it looks like code.

Screenshot 2017-08-17 at 10.27.28

Maxwell’s equations

But even without the maths, we can understand what the equations mean. Continue reading

A Map of Physics

In 1966 Richard Feynman gave an interview about teaching physics. He described a problem with physics teaching: often students did not know where they were:

In other words, there always should be some kind of a map. – Feynman

The book I am writing for novice teachers is built around a map. I started by writing the text for a timeline for five big ideas of physics: space, electricity, forces at a distance, particles and energy. It was tricky, because several of the timelines intersected at points. So this morning I designed my physics metro-map. I have written a text for each of the stops, some of which I have already published (e.g. here, here, here).

Map of Physics

A Metro-Map style map of physics – each stop has a short text to explain the physics.

The book containing the interview is Feynman’s Tips on Physics. It follows on from his lectures. He deserves his reputation as an excellent teacher. One of the fascinating things in Tips on Physics is his emphasis on solving problems. In other words, Feynman was bang on Cog-Psy message 50 years ago. 

Better than Wrong

Science exams are typically examples of the difficulty model of assessment where answers are right or wrong (see Christodoulou, Making Good Progress chapter 3). Assessors can use a marking rubric to judge whether an answer reaches a threshold of ‘correctness’ and award or deny a mark.

For many answers, this will be uncontroversial. However, some answers are less wrong than others: some answers are better than wrong.

A colleague and I took a single sentence answer from an end of year exam that many students got wrong, but which weren’t uniformly wrong.

A mark-scheme is binary: right or wrong, but we wanted to know whether we could do better than that: could we rank the answers? Could we identify which answers were almost there?

The answer is yes, and pretty reliably, using comparative judgement.

Comparative judgement (CJ) is a method for ranking and assigning a score to writing by comparing two pieces at a time. All the judge needs to do it decide which of the two is better and then repeating. Typically this is done with longer texts (we will try using long answers after the summer). But I was particularly interested in seeing what happens when you compare single sentences.

You can try for yourself here.

Typically, for longer pieces of writing, you get a fairly even distribution of scores. This didn’t happen here.

CJ task #1 Better than Wrong (1)

The results show three populations of answers: right, wrong and better than wrong.


  1. For some questions, students should simply learn the approved answer. Definitions are a good example of this.
  2. Binary right/wrong answers often fail to pinpoint students’ understanding/misunderstanding.
  3. To do this process routinely for individual questions would be too time consuming, but it was a short instructive activity for teachers before discussing better ways of teaching the concept .

Thank you to all of the additional teachers who helped with the judgements.

The data is here.

Using Physics Questions to Build Problem Solving, Literacy and Knowledge.

A few weeks ago I observed an English teacher pull a sentence apart. A line from Romeo and Juliette was on the board and the class spent ten minutes together identifying the parts of speech (verb/noun/particle etc); the effect of words on the reader (to connote is a verb – I didn’t know that) and language techniques (repetition, alliteration, rhyme, personification etc). They marked it all up on the board. The students were practising marking-up the same sentence on paper (board=paper from Teach Like a Champion 2.0).

I thought it was like looking at a diagram goal free . Without worrying about the question at first, students were laying down all of the information they could about the line.

Then, as a class, they began to add the context. The result was an exploded sentence, with all of the bones exposed.

They answered questions about the line.

I wondered whether I could do something similar with a physics sentence – specifically an exam question. Instead of looking at the language techniques, I would pull apart the vocabulary and knowledge.

So I took some exam papers and chose a couple of questions to try.

The first obvious thing is that for GCSE physics questions (especially higher tier), single sentence questions are rare. Also, many questions have diagrams:

So I split the task into several parts. First, we went ‘goal-free’ on the diagram, which took 5 minutes using a think-pair-share.

goal-free 1-page-001

Goal-Free exploration of the diagram using Think-Pair-Share activity

(AQA Physics Unit 1 June 2016)

We did a mini control-the-game (Reading Reconsidered) on the opening line (you can see the mark-up we did on vacuum below).

Finally, we got to the close-reading of the question line. I think the student’s marked-up sheet explains what we did as well as I could write it. It was a collaborative effort – I asked students to do this in pairs and then we shared. I was modelling on the board.

Then they answered the question.

kettle close-read-page-001

A close-read of the question followed by a write/rewrite (see TLaC and Reading Reconsidered by Lemov)

We shared and read the mark scheme and the students did a rewrite.

The whole task took 20 minutes, which is a big investment for one question. But I recommend doing it regularly because it does three things:

  1. It exposes students to both technical and non-specialist vocabulary, in a physics context, over and over again. You don’t need to plan and track the high mileage non-specialist words – they come up naturally. Technical words are also experienced, in context, over and over again, building understanding.
  2. It teaches student how to read a question.
  3. It teaches students how to write a good answer.

This sequence is an effective and simple way to develop literacy in physics lessons. It does several jobs pretty well. With practice, you might be able to get the whole sequence down to 10/15 minutes – but I’m not there yet. I’d be interested to hear if anyone else tries it or does something similar.




If you want it here, don’t put it there.

Wall displays, formula sheets and placemats…

If you want students to commit knowledge to long-term memory, you shouldn’t put it on the wall.

wall display CLT diagram

Wall displays, formula sheets and placemats as external memory

When you put knowledge on the wall, students will make use of it. Using external memory is a tremendously helpful method of reducing cognitive load. They will learn how to use the information. But they won’t learn the things on the wall.

So if you want them to learn something, help them learn it. Keep the wall for other things.