Question

when a fan is not used its blades stay quite clean for long time however if it is used the blades become dirty in a few days give reason​

Answer 1

Answer:

Dust tend to settle on horizontal surface

in still air dust is thicker below heat height; most dust is from shed skin

When the fan operates there are 2 effect

# The air is moving so dust is brought to the fan

# The moving air can generate static electricity which attract the dust

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