People prefer to wear cotton clothes in summer season. This is due to the fact that cotton clothes are
- A.good absorbers of water
- B.good conveyors of heat
- C.good radiators of heat
- D.good absorbers of heat
Correct answer
Explanation
The correct answer is A, good absorbers of water. Cotton soaks up sweat well, and as that sweat evaporates from the cloth it takes heat away from the body and keeps us cool. In summer the body sweats to control its temperature. Cotton fibres are made of cellulose, which attracts water, and the fabric is porous, so it draws sweat away from the skin and spreads it over a large area. Evaporation needs latent heat, and that heat comes from the body, so the skin cools down. Synthetic fabrics such as polyester absorb little sweat, which stays on the skin and makes us feel hot and sticky. Option B is wrong because the comfort of cotton does not come from conducting heat; cloth in general is a poor conductor. Option C is wrong because cotton is not chosen for radiating heat; cooling here comes from evaporation of sweat. Option D is wrong because a cloth that absorbed more heat would make us warmer, which is why dark clothes feel hot in the sun. Exam tip: summer comfort: cotton absorbs sweat and evaporation cools; light colours reflect heat.
Practice Questions
View allConsider the following statement : "Atomic number of an element is a more fundamental property than its atomic mass." Who among the following scientists has made the above statement ?
- A.Dmitri Mendeleev
- B.Henry Moseley
- C.J.J. Thomson
- D.Ernest Rutherford
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In 1913 the English physicist Henry Moseley showed that atomic number, not atomic mass, is the fundamental property of an element.
Read the full explanation →How many Carbon atoms are present in a Pyruvate molecule ?
- A.2
- B.3
- C.4
- D.5
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Pyruvate, the ion of pyruvic acid (CH3COCOOH), is a three-carbon molecule. It is formed at the end of glycolysis, the first stage of respiration, which takes place in the cytoplasm of every living cell.
Read the full explanation →The energy of a photon, whose momentum is 10 MeV/c, where c is the speed of light, is given by
- A.10 MeV
- B.100 MeV
- C.1 MeV
- D.0.1 MeV
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For a photon, energy equals momentum multiplied by the speed of light, E = pc, so a momentum of 10 MeV/c gives an energy of exactly 10 MeV.
Read the full explanation →Cell wall is not present in cells of
- A.Bacteria
- B.Plants
- C.Fungi
- D.Humans
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Human cells, like all animal cells, have only a flexible plasma membrane on the outside and no rigid cell wall.
Read the full explanation →The enzymes which catalyze the same reaction but have different amino acid compositions are commonly referred as :
- A.Isoenzymes
- B.Isotopes
- C.Isomers
- D.Coenzymes
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Isoenzymes, also called isozymes, are different molecular forms of an enzyme that speed up the same chemical reaction but differ in their amino acid sequence.
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