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Question:
A razor blade is placed gently on a water surface. A charged body brought near the razor makes it move away.what is the difference between the bronze (which is used in the razor blade) and water? Is it related to the polarity of them?



Replies:
This is a very good example of surface tension at work. The razor blade is covered with a thin layer of hydrophobic lubricant, which is essentially invisible to the unaided eye. However, this thin layer of lubricant is able to support an electric charge so that the blade is repelled by a similarly charged body. The metallic composition of the blade itself has little effect. It's all on the surface. You can test this by first preparing a dilute solution of dish soap -- maybe about 10% soap in water. Then gently put a drop of the diluted soap on the surface of the water holding the razor blade. I think you will see the blade sink very quickly because the surface tension supporting the blade is weakened and can no longer hold the weight of the blade.

Vince Calder



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