Electrostatics and the school science curriculum
Electrostatics is a topic that sits awkwardly in the school science curriculum. In fact, it is hardly a topic in itself before it is introduced in all its mathematical glory in grade 11. Until then, students normally only encounter a handful of scattered electrostatic facts and phenomena without getting the opportunity to make meaningful connections.
As a student, I had carried out the ubiquitous experiment of rubbing a plastic ruler on my hair and seen little paper bits get attracted to it. I was told that this happened because the plastic ruler had become electrically charged. I was told that there were two kinds of charges, one was called positive and the other, negative. I was also told that the same kind of charges repelled each other and the opposite kinds attracted each other.
There seemed nothing unusual about all this, and I was happy to accept it as the truth. Many years later, I realised that perhaps it was the analogy with the easily observable magnetic poles that made it so easy to unquestioningly accept the existence of two kinds of electrical charges and their behaviour. (There is a fascinating historical connection here, which I will examine in an upcoming sequel.)
As an extension, the metal-leaf electroscope was touched upon, and so too the fact that lightning was a strong discharge of static electricity. That was all the electrostatics I learnt until grade 10, and I’m sure most others did, and continue to do today as well.
The neglect of electrostatics is not surprising at all when you look at the electrical devices around. Whether it is a lamp, a motor, a heater or a computer, almost all the devices we use work on electrical currents. There is a closed circuit involved, and there is electricity in motion. There are hardly any electrical devices in daily use where electrostatic charges build up and attract tiny bits of paper (old CRT-televisions being a notable exception, of course).
A blanket on fire and electrified children on chairs!
I grew up in the humid coastal state of Kerala. It was at the age of 22 that I moved to Pune for work. There, I first experienced a dry winter — when the relative humidity could fall as low as 20%. And one night I discovered that this had other ramifications apart from having to apply petroleum jelly to avoid cracked lips.
That winter, I was using a coarse woollen blanket provided by the school to cover myself while sleeping. One night, I woke up feeling cold. The blanket had slipped off my body. As I pulled the blanket back over me, I was dazzled by an intricate web of dim yellow sparkles emanating from the blanket. There was also a faint crackling sound.
Initially I thought I was dreaming and I pinched myself to check if I was. And no, the sparkling and crackling were real!
The next day, I spoke to a friend and colleague — also a science teacher — about what I saw. He explained to me that the extremely low humidity made it possible for electrostatic charges to accumulate to very high potentials, making such brilliant discharges possible.
I came to know from him that some children in the school had found innovative ways to have fun during dry weather. They would make one person sit on a plastic chair with her legs folded up. Another person would hit the back of the chair many times with a woollen sweater. Then, when you touch the person sitting on the chair, you get a strong shock that makes you jump!
It all started with electrostatics
All this piqued my curiosity immensely and I was lucky to find two indispensable sources to learn more about electrostatic phenomena. One was the BBC Four documentary series – Shock and Awe: The Story of Electricity hosted by Jim Al-Khalili, and the other was the Harvard Case History on the development of the concept of electric charge.
And what I learned from these sources completely turned the tables on what I thought I knew about electricity. For the first 200 years or so of its development (roughly 1600-1800), ‘electricity’ meant electrostatic phenomena. There were no batteries, no motors, no devices that you would recognise today as ‘electrical’. And an awful lot was discovered about electricity during this time.
This made me wonder if it was possible to approach the teaching of electricity in school from an entirely different angle. One that paralleled the historical development of ideas, and drew on those stories of discovery.
This was 2011, I was teaching chemistry to grades 9 and 10, and I wasn’t able to actually try this out. In 2013, I left teaching to explore other areas of work. However, I did return to teaching in 2016 and this time I had grade 6 science to teach. Exactly the age group I wanted to explore electrostatics with.
In the coming posts, I intend to document my attempt at teaching electrostatics using a historical approach to eager 11-year olds.