Don’t Teach from Definitions! Just Don’t.

frustrated student

I settled down to watch a TV programme about schools, “Living with the Brainy Bunch”. It’s not something I would normally do having worked in schools for 13 years, a bit too much of a bus man’s holiday. The premise of this show was, however, intriguing. Two failing students were going to spend time living with a top grade student and their family to see if this would improve their prospects. How very Pygmalion. I was genuinely interested to see what the outcome would be.

But then in the middle of the documentary I found myself shouting at the TV screen. A teacher in the background of one scene committed the cardinal sin of physics teaching. The title of the lesson and aim were up on the board and the first thing they did was say “this is Ohm’s Law” and wrote it down, V=IR. Noooooooooooooo!


What is Wrong with Definitions?

There is a wealth, a plentitude, an embarrassment of research which clearly shows that rote physics teaching achieves poorer results in the short, medium and long term compared with active learning. This article published in Nature in 2015 summarises developing thought on the subject.

The rote style of teaching is adopted by people rushed for time, overly reliant on the exam specification or who don’t know what good physics teaching looks like. It makes for lessons which are instantly forgettable and do nothing to develop the students’ understanding. And understanding not parrot-fashion learning is crucial. The bread and butter basics of physics teaching should be understanding and thinking skills.

Charles Tracy and Peter Main from the Institute of Physics wrote an article called “Defining physics”[1] and have suggested a rather long winded but none the less instructive way of thinking about what physics actually is. Peter Main outlines his definition of physics as

a way of thinking, a reductionist view of the world where phenomena can be understood in terms of a relatively small number of physical laws and limited only by the complexity of a system or phenomenon. [2]

He argues that defining physics by its content misses out the crucial ways of thinking that studying physics should develop (when done correctly). Why develop these ways of thinking? Because you can’t DO physics in any effective way at all without developing these ways of thinking. Tracy and Main include critical thinking, deep understanding, logical and experimental consistency, use and development of models, awareness of simplifications, the excising of prejudice in thought patterns and ability to go beyond “common sense” in their list of physics skills. None of these are being taught or practised when teaching is done by copying a definition in words and symbols and then applying it to examples.

Teaching from definitions is teaching content only, and in the most dry and uninteresting way. You remove all thinking for the students and present a fait accompli. Effectively you are conveying this message “some other smart people came up with this, I’m not going to tell you how, just shut up and learn it OK?”. You do this and you are a disgrace to the profession.

Telling a student an answer, e.g. plug it in V=IR, and you enable them to solve a single set of simple problems. Explain to them how and why V=IR came about and they have an understanding that will enable them to solve many problems. Allow them to discover the relationship for themselves and work out how to use it and you’re a bloody genius. This is what we should all be doing in our classrooms.


Teaching from Definitions and the Impact on Girls

Teaching from definitions is stated by female students as one of the things which turns them off physics. This was an interesting outcome from the research “Girls in the Physics Classroom”[3].  From that publication note this particular quote:

Physics makes greater use of precise technical language and symbolic representation than the other science disciplines – probably than all other school subjects apart from mathematics. Most physics teachers are steeped in the use of, and sometimes the abuse of, this type of language. For example, it is not uncommon to hear “V = IR” used to denote Ohm’s law. For many pupils – boys and girls – this use of language and symbols is mystifying and it reinforces the impression that the subject does not connect with their world. Teachers who “talk equations” at an early stage in physics education risk alienating many students – girls in particular – from the subject.

The author goes on to say how pupils at KS4 begin to heavily link maths to physics but not because they are frequently using maths in analysing data or solving problems. No they get used to being presented with equations out of a useful context.

“It’s all about remembering equations. I can work out the resistance of a wire but I don’t know what it means.”


Girls especially found that this was a problem because they felt unable to “ask questions about a word or equation” and so felt that their understanding was stalled. Teachers who only introduced equations once the underlying concepts were well established were able to keep girls’ interest for longer.

It is important to understand that the reluctance of girls to engage with technical shorthand language is not a result of their reduced understanding. Indeed the author stresses that when questioned by the researchers the girls had an equal understanding to their male peers. Historically girls outperform boys in GCSE science including physics. In 2016-2017 169,455 girls achieved A*-C in maths and science GCSE compared to 163,256 boys [4].

The difficulty appears to be cultural. Boys are cultured to use technical language and be rewarded with peer status and the approval of older authority figures when they do. Think about how boys discuss football stats or the specifications of their mobile phones, cars, computers. They spend years developing a confidence with numerical shorthand and technical language in competitive communications with their peers. Girls are socialised to use more expressive and empathetic language. I can’t tell you how weirdly you are treated as a young woman if you try having a conversation about the amount of memory, processing speed and other specifications of a tablet, laptop or phone. Bafflement not at the content of the conversation but at my motivations, awkward silences and “what is wrong with you?” are all responses I have had when trying to talk geek to other girls.

When a teacher uses technical language and algebraic shorthand in a physics class they are unwittingly displaying a bias in favour of one gender. The use of a snappy V=IR shorthand feels instantly familiar to boys. Girls aren’t familiar with this way of speaking and seem uncomfortable with using it, holding back their replies. Then a boy shoves up his hand or calls out and gives a terse one word reply, the teacher accepts it and the lesson moves on. But you have lost the interest of the girls. Overtime this communication bias leads them to give up on answering questions in class. They feel less able to access the lesson and join in the teacher-pupil conversation.

The advice from the report was as follows:

Teachers, both male and female, in the most successful schools made more sparing use of technical language, used terminology in context and avoided algebraic shorthand. They used everyday language wherever possible and, where terminology was needed, it was carefully defined and pupils’ understanding was checked…


…The guiding principle was to establish ideas and concepts before the use of terminology or equations.

Once understanding is established the teachers introduced the terminology and rigorously policed its correct use. No sloppy reference to “electricity” when “current” is the word required.

It can’t be overstated how much the use of language effects students studying science. Too much technical jargon and it feels more like a foreign language lesson than something relevant to real life. As one girl in the report says:

“If physics is relevant then we ought to be able to talk about it using normal language. I used not to ask questions because I didn’t know how to put them – I didn’t have the right words. [Teacher X] doesn’t mind this and encourages us to have a go. If we use the wrong words [Teacher X] doesn’t correct us or make us feel embarrassed.”

We need to make our lessons as inclusive and easy to comprehend as possible. That doesn’t mean leaving out technical scientific terms. It does mean developing the understanding first through direct experience of the phenomena and its applications then slowly building in the correct language and algebraic shorthand once this is established.


The Importance of Discussion, Analogy and Relevance

Before students can develop a facility with technical language they need to have a handle on the topic. This means discussions about the uses and phenomena associated with the topic. How discussion is done in a classroom can vary. Little or no discussion takes place in rote lessons. The teacher asking a closed question “what is ….” and getting a terse response is not discussion.

To aid context and understanding students need time to explore what they know about a topic amongst themselves. Small group discussions work well when combined with the requirement to produce a group response or an answer on a small white board. Questions like “What is it about electricity that makes it so useful to us?”; “What happens when we turn a light switch off?”; “Why do we have to have a system of pylons and cables around the country?”; and “Why can’t we store electricity?” are so much more useful than “what is the definition of current?” [3].

This discussions and group responses can all occur using ordinary language. Then the teacher can lead the whole group in the development of these ideas. “Why can’t we store electricity?” is bound to lead to a discussion of the role of a battery in a circuit. From this charge separation, electric fields and the transfer of energy through the movement of charges in a wire can all be demonstrated and explained.

Mental images of what is going on are very useful, particularly in some topics. Electricity is notoriously lacking in direct visual input, and so requires a suitable analogy. All students benefit from this but teachers need to be careful they don’t use out of date or again biased examples. As one female student says “I’m not interested in how Beckham bends a ball or what the acceleration of a Ferrari is – why should I be?”. An even better approach is to see if students can devise their own analogies. All of this aids understanding and model building before any equation needs to be introduced.

I would leave equations until after the students have done an experiment or seen a demonstration where the relationship of interest is clearly shown. It is so much easier to infer and remember a result from data you have collected yourself. Set up a simple circuit with a resistor. Take some readings, plot a graph, draw a gradient. Then introduce Ohm’s Law.

Lastly, understanding is aided when physics is contextualised. It is a mistake to assume all students want modern, real world examples when asking for relevance. What is relevant can vary from person to person. It is enough to say that a topic is relevant because it helps explain X, Y or Z. Or maybe it connects with some wider moral or philosophical issues (origin of the Universe), some ethical argument (use of nuclear power), even a conspiracy theorist’s misunderstandings (climate change). They may well want to hear about applications of this topic in their daily lives but they also like to know about applications beyond their limited experiences. Sometimes it is relevant because it is the pathway to a desired career goal, relevant in a pragmatic way. If you wish to study architecture, physics can be relevant even if not everything is about the construction of buildings.


The Death of Definitions

I started out by saying teaching from definitions is a method used by rushed teachers, those reliant on the specification and those who don’t understand how best to teach.

What if you are rushed for time? The curriculum demands increase year on year and sometimes cramming triple science GCSE into a double science timetable requires corners to be cut. So cut the definitions. Teach circuits with circuits even if you have to demonstrate rather than do a class practical. Get students to take the readings with you, volunteers can write the data up on the class board. They can still work out the relationships you need individually and they will learn as they do.

People are often told “don’t teach to the specification” I think this doesn’t go far enough. Some people actually teach the specification. There is nothing wrong with using this document to guide your lessons but you don’t get students to work through 3-4 points from the spec each lesson. It is a check list to ensure you cover each point, not an instruction manual. Teaching from specification or textbooks indicates lack of confidence.

The best remedy to lack of confidence in physics teaching is to find out how to teach the subject from an expert. Buy a good book, enrole on a CPD course or get support from physics specialists in your school or online, for example TalkPhysics.

Or you could keep reading the articles on here, The Physics Teacher.



[1] Main, P. C. and Tracy, C. M. (2013) “Defining physics.” Physics World, 26(4), 17–18

[2] Main, P.C. “Thinking Like a Physicist: Design Criteria for a Physics Curriculum”  Schools Science Review March 2014, 95(352)

[3] “Girls in the Physics Classroom” 2006,

[4] viewed 14/7/2018

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