What type of car does an electrician drive? A Volts-wagon!
I need a joke to cheer me up as it’s year 7 electricity time again. As a Physicist I should relish this topic, but it doesn’t seem matter how many times I’ve checked the lamps and connections; the start of any practical lesson is beset by cries of “It won’t work Sir!” from all corners of the room. I’ve taught in seven different schools now, all quite well equipped with a different electricity “set” in each case, and none of them work very well. Even when they do work, how do you explain why two apparently identical bulbs in a series circuit can shine with different brightnesses to a year 7? As sometimes occurs in Science, the practical can come between the students and their understanding. As an NQT I used to do as much practical as possible, but as I’ve got older (and lazier) I’ve tried to target my practical work much better, with understanding being the top priority.
Students are confused by words like “charge”, “current” and even “electricity” (whatever that is). Why not simply talk about the movement of electrons – even lower down the school in year 7? It is much easier for students to visualize a flow of particles carrying energy than it is to comprehend vague expressions like “flow of charge” or to understand current as a flow of water etc.
I now try to eliminate or reduce the building of circuits by using role play instead. This not only avoids the chaos described above, but also leads to deeper understanding.
I make lots of small pieces of paper (about 1 cm x 5 cm) and arrange the students around the room in a large circle with me at one side (with the paper) and a lit Bunsen on the other (with plenty of mats surrounding it!). The students walk slowly round the room, collecting a piece of paper from me, setting light to the paper at the Bunsen (and placing on the mats) and returning to get more. I ask them in groups to try to identify the elements in the circuit (perhaps by sketching). I am the cell (use correct terminology here!), they are electrons, the Bunsen is a lamp and the paper is energy.
I then use a technique called “Draw the sentence” to assess their understanding. The main points of the lesson are written as sentences (e.g Current is the flow of electrons. The electrons carry energy from the cell to the lamp. The electrons then return to the cell to get more energy etc.). The students divide a sheet of paper into 8 and have to “draw” these sentences (one word per drawing allowed). It is useful to demonstrate this to the class first; I draw humorous sentences about myself which normal reference my love of Nottingham Forest and hatred of dogs which they have to guess.
Subsequent lessons can then focus on current in series and parallel circuits (using the role play), voltage, power and resistance, making sure each concept is clear before moving onto the next. Pretty much every electrical phenomenon right up to year 13 can be dealt with using this simple analogy. At sixth form you should emphasise that it is a useful model but not reality, extending more able Physicists by getting them to explore the limitations of the analogy and explaining the actual nature of electron potential energy in an electric field.
Having written this, I feel a little happier about next week’s year 7 electricity topic, although no less trepidatious about the year 7s themselves!
Simon Porter teaches physics for premium international schools organization Nord Anglia Education.