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Science — UPSC Prelims MCQs

1,120+ practice questions across 14 chapters, including 303+ previous year questions— each with option-by-option explanations.

Chapters in Science

Sample Science questions

A preview of the kind of MCQs you'll practise — with the correct answer and explanation.

Q1ScienceEnergy, Nuclear and Material Science

Consider the following statements about 'nuclear magnetic resonance' (NMR): 1. It exploits the magnetic properties of atomic nuclei to determine physical and chemical properties of atoms or molecules. 2. MRI (Magnetic Resonance Imaging) used in medicine is based on NMR principles. 3. NMR can only be used on radioactive materials. Which of the statements given above is/are correct?

  • A1 only
  • B1 and 2 onlyCorrect
  • C2 and 3 only
  • D1, 2 and 3

Explanation

Correct. NMR uses the magnetic behaviour of nuclei (especially hydrogen) to study molecular structures, and MRI is its medical imaging application. Statement 3 is wrong; NMR works with stable isotopes like hydrogen-1 and carbon-13, not radioactive materials.

Q2ScienceBiotechnologyPYQ 2020

With reference to carbon nanotubes, consider the following statements: 1. They can be used as carriers of drugs and antigens in the human body. 2. They can be made into artificial blood capillaries for an injured part of the human body. 3. They can be used in biochemical sensors. 4. Carbon nanotubes are biodegradable. Which of the statements given above are correct?

  • A1 and 2 only
  • B2, 3 and 4 only
  • C1, 3 and 4 onlyCorrect
  • D1, 2, 3 and 4

Explanation

Correct. Carbon nanotubes serve as drug/antigen carriers, function in biochemical sensors, and certain forms are biodegradable through enzymatic action. They have not been made into artificial blood capillaries.

Q3SciencePlant Biology and Applied Biology

Gibberellins are best known for their role in:

  • APromoting fruit ripening and leaf abscission
  • BInducing stem elongation and breaking seed dormancyCorrect
  • CCausing root initiation in cuttings
  • DTriggering stomatal closure during drought

Explanation

Correct. Gibberellins promote internode elongation (causing bolting in rosette plants), break seed dormancy by inducing α-amylase synthesis, and stimulate flowering in some long-day plants.

Q4ScienceCell Biology and Genetics

Which of the following organelles is responsible for the synthesis of lipids and detoxification of drugs in the cell?

  • ARough endoplasmic reticulum
  • BSmooth endoplasmic reticulumCorrect
  • CGolgi apparatus
  • DPeroxisome

Explanation

Correct. Smooth endoplasmic reticulum lacks ribosomes and is the primary site for lipid synthesis, steroid hormone production, and detoxification of drugs and poisons.

Q5ScienceChemistry in Everyday Life

Hard water does not lather easily with soap because:

  • AHard water contains dissolved oxygen which reacts with soap
  • BHard water contains calcium and magnesium salts which form insoluble compounds with soapCorrect
  • CHard water has a higher density than soft water
  • DHard water is alkaline in nature and neutralises the soap

Explanation

Correct. Hard water contains dissolved calcium and magnesium ions (from bicarbonates, chlorides, or sulphates) that react with soap (sodium stearate) to form insoluble calcium/magnesium stearate (scum), preventing lather formation.

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