Why does dust get deposited only on one side of the blades of a fan ?

1.	Why does dust get deposited only on one side of the blades of a fan ?
Answer» Blades of a ceiling/table fan have uniform thickness (unlike that of an aerofoil) but are angled (cambered) at 8° to 12° (optimally, 10°) from their plane. When they are set rotating, this camber causes the streamlines above/behind a fan blade to detach away from the surface of the blade creating a very low pressure on that side. The lower/front streamlines however follow the blade surface. Dust particles stick to a blade when it is at rest as well as when in motion both by intermolecular force of adhesion and due to static charges. However, they are not dislodged from the top/behind surface because of complete detachment of the streamlines. The lower/front surface retains some of the dust because during motion, a thin layer of air remains stationary relative to the blade.

Answer»

Blades of a ceiling/table fan have uniform thickness (unlike that of an aerofoil) but are angled (cambered) at 8° to 12° (optimally, 10°) from their plane. When they are set rotating, this camber causes the streamlines above/behind a fan blade to detach away from the surface of the blade creating a very low pressure on that side. The lower/front streamlines however follow the blade surface. Dust particles stick to a blade when it is at rest as well as when in motion both by intermolecular force of adhesion and due to static charges. However, they are not dislodged from the top/behind surface because of complete detachment of the streamlines.

The lower/front surface retains some of the dust because during motion, a thin layer of air remains stationary relative to the blade.

Discussion

No Comment Found

Related InterviewSolutions

What were the two main occupations of the Rig Vedic Aryans?
Name the two political institutions which exercised check on the powers of the King in the Rig Vedic period.
What w’as the position of women in the Rig Vedic age ?
Describe the social life of the Rig Vedic Aryans with reference to the following: (a) The Family Structure (b) Position of Women (c) Varna System
With reference to the following explain the main features of the Rig Vedic Economy: (a) Agriculture (b) Domestication of Animals (c) Trade Transactions, Crafts and Transportation
Mention any two archaeological sources to reconstruct the later Vedic Age.
Mention any two of the Ashrams in the life of a man in Aryan society.
What information do we gather from the later Vedic literature in respect of: (a) Spread of Vedic Civilization to many New Regions. (b) Role of Iron in later Vedic Economy.
Mention briefly the rituals and sacrifices of the later Vedic Aryans?
What is the message of the Bhagavad Gita?