December 2012

Physics in Everyday Life: The physics of static electricity…

A few weeks ago I was approached by a reporter from a local Chinese newspaper – Ming Pao Newspaper – Ms. Louisa Chan. She asked me to clarify a few questions asked by their readers: specifically she wanted to know more about the electric shock and why it happens more often in the winter than in the summer. I thought it was a good science question and based on our conversation she was able to write a response in her newspaper. I do not know if you will be able to read it, but just in case… The reason that in the winter we get shocked more often is that we have low humidity in homes and electrical charge doesn’t have an opportunity to leak off as easily as it can do in the summer. Low humidity happens here because we heat up the air in our homes. Hot air will have much less humidity than the cold one, because the same amount of water in the water-air mixture will mean different humidity values at different temperatures. In general, hot air can hold much more water vapour in the air-water mixture, than the cold one… So if you want to know more about it, then look up a term “psychrometric chart”. It will help you  understand the humidity concept… And if you still wonder how humidity is measured, then loop up a term – hygrometer  – a device that measures humidity and how it works. Understanding it you will also be able to appreciate why we need a humidifier during winter time and why we rarely need it in the summer…

And if you read Mandarin, you probably will be able to read it and maybe you will tell me if what is written in the newspaper is a good explanation of this concept… I couldn’t discern anything except for my name and a few numbers.


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