Equation-centric physics teaching – why I’m leaving it behind.

“Physics is boring.”, “Physics is hard.”, “Physics is just remembering all the equations.” Comments I have heard all too often from students. I’ve been thinking about why many students have this perception of physics, whether it’s justified, and how we might be able to move away from it.

With the increased requirement for students to memorise equations, and the large percentage of marks in GCSE papers devoted to their recall and use (well over 30% in 2019 AQA GCSE Physics papers), it’s no surprise that teachers are tempted to focus on equations. I’ve certainly been guilty of this. In the 2019 AQA Physics papers a student scoring full marks on all the calculation questions, while leaving the rest of the paper blank, would have achieved a Grade 5 – what further justification of the importance of equations is required, you might ask? I’m certainly not advocating forgetting about equations, or saying that they’re not important, but it’s very easy to think (especially for non-specialist teachers) that the equation is king. If students can recall equations and plug in the correct numbers then they’ve got it, they’ve understood electricity (V = IR), forces (F = ma), waves (v = fλ). The list could go on and on. This is clearly far from the truth, but it’s often the way students think because it’s the way physics is taught.

The ability to remember and apply the correct equation is a necessary skill and might get lots of exam marks. However, it is robbing students of their entitlement to a real understanding of the physical world, and I suspect that an emphasis on equations in teaching is, at least partly responsible for the prevalent view amongst students that physics is ‘boring’ – who wouldn’t quickly get tired of plugging apparently random numbers into formulas to calculate values which have no real meaning if the physics behind the equations has not first been understood?

Hearing Tom Sherrington speak at ResearchEd Surrey sparked off this train of thought. He spoke about the importance of experience and knowledge in the context of the motor effect and the equation F = BIL (also see here). Students need to experience magnets, motors, the interplay between electricity and magnetism and the influence of a magnetic field on a current carrying wire, before they can really grasp the motor effect, or understand F = BIL as more than an abstract formula. They need to handle these things, experience them and see the effects of changing the parameters, not in a “discovery learning” – go away and ‘reinvent the motor’ or ‘rediscover the relationship’ – sort of way, but in the sense of having a concrete feel for the physical phenomena which underpin the workings of the electric motor and the interactions between them. Giving students opportunities to develop the tacit knowledge which is gained from hands on experience is so important. We need to alter our approach so that when I teach Year 13 electromagnetism my students’ first response is no longer, “Oh yeah, Miss, we know all about this, ‘F equals Bill’.”! Especially as, when I probe beneath the surface, this seems to be the extent of their knowledge – a memorised equation with little or no underlying substance.

I started to think about other equations and whether I was guilty of an equation-centric approach. The answer is yes. I’ve definitely introduced new concepts through the equation rather than focusing on developing students’ understanding of the underlying physical concepts and the relationships between them, before adding in the equation as a means of quantifying this. Equations enable you to find the size of physical parameters. But for the development of a sound schema the underlying concepts and understanding are of fundamental importance. When we focus on the equations and plugging endless numbers into calculators, we are denying our students the opportunity to really grapple with the physical realities which these equations describe. Wherever possible we should begin physics teaching by developing an understanding of the concept only adding in the numbers when this is understood.

I’ve started to think through a couple of topics with this approach which I have outlined below. I’ve found it helpful to map out the knowledge which underpins each equation, before thinking about a teaching sequence to revisit or teach this information and build up an understanding of the physical realities of the equation only introducing numerical examples at the end.

Example 1: Newton’s second law of motion

Example 2: Ohm’s Law

The equation shouldn’t lead the learning – the conceptual physics is what will enable students to understand and explain the world around them, equations are just a way of quantifying the parameters involved.

Equations might be boring, physics certainly is not!

2 thoughts on “Equation-centric physics teaching – why I’m leaving it behind.

  1. Thank you for this. I have taken a similar approach to you with F=ma for a few years, but the V=IR method will help me reframe my teaching next time around.

    Something I like to do is teach enough of the concept that students can end up deducing the relationship between, e.g. wavespeed,wavelength and frequency themselves rather than me put it in the board and get them to copy. I feel that when students can deduce the relationship they have fully learnt the concepts behind it and also are less like to make errors when recalling it in an exam. Not possible for all equations (kinetic energy for e.g.) but for many this works well.

    Like

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