Science & Technology

CDS 202537 questions

1. Q1

   The rule to determine the direction of a current induced in a coil due to its rotation in a magnetic field is :

   • ARight-Hand Thumb Rule.
   • BFleming's Left-Hand Rule.
   • CFleming's Right-Hand Rule.
   • DHund's Rule.
   Show answer & solution

   Correct answer: (C) Fleming's Right-Hand Rule.

   Fleming's Right-Hand Rule gives the direction of the induced current (or induced EMF) when a conductor moves in a magnetic field, which is exactly the case of a coil rotating in a field (a generator/dynamo). Fleming's Left-Hand Rule applies to the force on a current-carrying conductor (motor action), the Right-Hand Thumb Rule gives the field around a current, and Hund's Rule concerns electron filling of orbitals.

2. Q2

   A car travels a total distance L. It travels half the distance with speed v1 and the other half with speed v2. The average speed of the car is :

   • A(v1 + v2)/2
   • B2v1v2/(v1 + v2)
   • C(v1 + v2)L / 2v1v2
   • D0
   Show answer & solution

   Correct answer: (B) 2v1v2/(v1 + v2)

   For equal distances covered at two speeds, the average speed is the harmonic mean: total distance divided by total time. Each half L/2 takes time (L/2)/v1 and (L/2)/v2, so average speed = L / (L/2v1 + L/2v2) = 2v1v2/(v1 + v2). The simple arithmetic mean (v1+v2)/2 is wrong because more time is spent at the lower speed.

3. Q3

   The linear momentum of a particle is conserved if :

   • Athe net force on it is maximum.
   • Bthe net force on it is zero.
   • Cthe net torque on it is zero.
   • Dthe net work done on it is maximum.
   Show answer & solution

   Correct answer: (B) the net force on it is zero.

   By Newton's second law in the form F = dp/dt, the rate of change of linear momentum equals the net external force; if the net force is zero, momentum stays constant. Torque governs angular momentum, not linear momentum, and work relates to energy, so those options are irrelevant to conservation of linear momentum.

4. Q4

   When a stone tied to a string is whirled in a circle, the work done on it by the string :

   • Ais positive.
   • Bis negative.
   • Cis zero.
   • Ddepends on the mass of the stone.
   Show answer & solution

   Correct answer: (C) is zero.

   The string's tension provides the centripetal force, which always acts along the radius toward the centre and is therefore perpendicular to the instantaneous velocity (and displacement) of the stone. Since work = force times displacement in the direction of force, and the angle is 90°, the work done by the string is zero regardless of the stone's mass.

5. Q5

   Assume 'A' does 500 J of work in 'x' minutes and 'B' does 1000 J of work in 20 minutes. If the power delivered by 'A' is P1 and 'B' is P2 and P1 = 2P2, then 'x', in minutes is :

   • A10
   • B5
   • C20
   • D25
   Show answer & solution

   Correct answer: (B) 5

   Power is work divided by time: P1 = 500/x and P2 = 1000/20 = 50 J/min. The condition P1 = 2P2 gives 500/x = 2(50) = 100, so x = 5 minutes.

6. Q6

   A sound wave travelling at a speed of 330 m/s produces 20 crests and 20 troughs in 0·1 second. The wavelength of the sound wave is :

   • A1·1 m
   • B3·3 m
   • C1·65 m
   • D2·2 m
   Show answer & solution

   Correct answer: (C) 1·65 m

   Each full wavelength contains one crest and one trough, so 20 crests and 20 troughs mean 20 complete waves pass in 0.1 s, giving frequency f = 20/0.1 = 200 Hz. Wavelength = speed/frequency = 330/200 = 1.65 m.

7. Q7

   An X-ray can be deflected :

   • Aby a magnetic field.
   • Bby an electric field.
   • Cby both electric and magnetic field.
   • Dneither by electric field nor by magnetic field.
   Show answer & solution

   Correct answer: (D) neither by electric field nor by magnetic field.

   X-rays are electromagnetic radiation and carry no electric charge, so they experience no force from electric or magnetic fields and cannot be deflected by them. Only charged particles (like electrons or protons) are deflected by such fields.

8. Q8

   In a simple astronomical telescope, the objective and the eyepiece used respectively, are :

   • Aa convergent lens and a divergent lens.
   • Ba divergent lens and a divergent lens.
   • Ca divergent lens and a convergent lens.
   • Da convergent lens and a convergent lens.
   Show answer & solution

   Correct answer: (D) a convergent lens and a convergent lens.

   A simple astronomical (refracting) telescope uses a convex (convergent) lens as the objective to form a real image of the distant object and another convex (convergent) lens as the eyepiece to magnify that image. Hence both lenses are convergent.

9. Q9

   Twinkling of a star is due to :

   • AInterference of light
   • BRefraction of light
   • CPolarization of light
   • DDiffraction of light
   Show answer & solution

   Correct answer: (B) Refraction of light

   Starlight passes through atmospheric layers of continuously varying density and temperature, so it undergoes fluctuating atmospheric refraction; the star's apparent position and brightness keep shifting, which we perceive as twinkling. It is not caused by interference, diffraction, or polarization.

10. Q10

    Van de Graaff generator generates :

    • Aelectrostatic charge
    • Bmagnetic field
    • Chigh voltage low alternating current
    • Dhigh voltage low direct current
    Show answer & solution

    Correct answer: (A) electrostatic charge

    A Van de Graaff generator accumulates and stores large amounts of electrostatic charge on a hollow metal dome, building up a very high electrostatic potential. Its fundamental function is to generate electrostatic charge, which is used to accelerate charged particles in physics experiments.

11. Q11

    Which one of the following metals is widely extracted by the electrolysis of its molten compound ?

    • ACu
    • BAu
    • CSn
    • DNa
    Show answer & solution

    Correct answer: (D) Na

    Sodium is a highly reactive metal that cannot be extracted by chemical reduction, so it is obtained industrially by electrolysis of its molten chloride (NaCl) in the Down's process. Less reactive metals like copper, gold, and tin are extracted by other methods (reduction, or found native), not electrolysis of molten salts.

12. Q12

    Which one of the following is not a property of 'graphene' ?

    • AIt is the thinnest material known so far.
    • BIt is almost completely transparent.
    • CIt is highly conducting.
    • DIt is a wide band-gap semiconductor.
    Show answer & solution

    Correct answer: (D) It is a wide band-gap semiconductor.

    Graphene is a zero band-gap (or semi-metal) material, not a wide band-gap semiconductor, so that statement is false. Its genuine properties include being the thinnest known material, nearly completely transparent, and an excellent electrical conductor.

13. Q13

    Why do plastics not degrade easily ?

    • AThey have strong ionic bonds.
    • BThey have strong covalent bonds.
    • CThey have strong metallic bonds.
    • DThey have very high melting points (> 500°C).
    Show answer & solution

    Correct answer: (B) They have strong covalent bonds.

    Most plastics are polymers held together by strong covalent bonds within long carbon chains, which are difficult for microorganisms and natural agents to break, so plastics resist degradation. They do not contain ionic or metallic bonds, and their non-degradability is due to bond strength and lack of enzymes to break them, not merely high melting points.

14. Q14

    Which one of the following is the correct chemical formula of carboxylic acid ?

    • AC3H7OH
    • BC3H8
    • CC2H5COOH
    • DCH3COCH3
    Show answer & solution

    Correct answer: (C) C2H5COOH

    Carboxylic acids contain the carboxyl functional group -COOH, which is present in C2H5COOH (propanoic acid). C3H7OH is an alcohol, C3H8 is an alkane, and CH3COCH3 (acetone) is a ketone, none of which contain the -COOH group.

15. Q15

    Which one of the following statements is not correct for benzene ?

    • AEach carbon atom forms sigma bonds with two other carbon atoms with a bond angle of 120°.
    • BDelocalized electrons create a symmetrical 'cloud' of electrons above and below the plane.
    • CThe length of C – C bonds is intermediate between single and double bonds.
    • DIt has six isomers.
    Show answer & solution

    Correct answer: (D) It has six isomers.

    Benzene (C6H6) has a single, unique symmetrical ring structure and does not have six isomers, so that statement is incorrect. The other statements are true: each carbon forms sigma bonds to two neighbouring carbons at 120°, the delocalized pi electrons form clouds above and below the ring plane, and all C-C bond lengths are equal and intermediate between single and double bonds.

16. Q16

    Which one of the following is not a nitrogen fertilizer ?

    • A(NH4)2SO4
    • BNH4NO3
    • CN2
    • D(NH2)2CO
    Show answer & solution

    Correct answer: (C) N2

    Nitrogen fertilizers must supply nitrogen in a plant-available form; ammonium sulphate, ammonium nitrate, and urea all do so. Molecular nitrogen gas (N2) is chemically inert and cannot be absorbed directly by most plants, so it is not a nitrogen fertilizer.

17. Q17

    Which one of the following general electronic configurations correctly represent a transition metal element ?

    • A(n – 2) d^(1–10) ns^2
    • B(n – 2) f^(1–14) (n – 1) d^(0–1) ns^2
    • Cns^2 np^6 nd^(1–10)
    • D(n – 1) d^(1–10) ns^(0–2)
    Show answer & solution

    Correct answer: (D) (n – 1) d^(1–10) ns^(0–2)

    Transition metals are the d-block elements, whose general electronic configuration is (n-1)d^(1-10) ns^(0-2), with the differentiating electron entering the (n-1)d subshell. The other configurations are incorrectly written (e.g., using (n-2)d or nd), and option involving (n-2)f represents inner transition (f-block) elements.

18. Q18

    Variable oxidation numbers are possible for :

    • ASodium
    • BCalcium
    • CIron
    • DLithium
    Show answer & solution

    Correct answer: (C) Iron

    Iron is a transition metal with partially filled d-orbitals, allowing it to show variable oxidation states such as +2 (ferrous) and +3 (ferric). Sodium, calcium, and lithium are s-block metals with fixed oxidation states (+1, +2, +1 respectively).

19. Q19

    Which one of the following gas smells like a rotten egg ?

    • AAmmonia
    • BHydrogen sulphide
    • CAcetylene
    • DSulphur dioxide
    Show answer & solution

    Correct answer: (B) Hydrogen sulphide

    Hydrogen sulphide (H2S) is the gas notorious for its characteristic foul smell of rotten eggs. Ammonia has a pungent choking smell, sulphur dioxide smells like burnt sulphur, and acetylene has a faint garlic-like odour, so none of these matches the rotten-egg smell.

20. Q20

    The chemical reaction K2SO4 (aq.) + BaCl2 (aq.) → 2KCl (aq.) + BaSO4↓ (solid) is an example of :

    • AAddition reaction
    • BDisplacement reaction
    • CDecomposition reaction
    • DDouble displacement reaction
    Show answer & solution

    Correct answer: (D) Double displacement reaction

    In this reaction the cations and anions of the two reactants exchange partners (K pairs with Cl, Ba pairs with SO4), which is the definition of a double displacement reaction; it is driven by the precipitation of insoluble BaSO4. It is not addition, single displacement, or decomposition.

21. Q21

    Which one among the following is the correct scheme followed for classification of animals ?

    • AClass → Phylum → Order → Genus → Family → Species
    • BPhylum → Class → Family → Genus → Order → Species
    • COrder → Class → Phylum → Family → Species → Genus
    • DPhylum → Class → Order → Family → Genus → Species
    Show answer & solution

    Correct answer: (D) Phylum → Class → Order → Family → Genus → Species

    The correct taxonomic hierarchy in descending order is Phylum → Class → Order → Family → Genus → Species. The other options jumble this sequence, e.g. placing Family before Order or Genus before Family, which violates the accepted Linnaean scheme.

22. Q22

    Which one of the following is an example of airborne disease ?

    • ATuberculosis
    • BMalaria
    • CDengue
    • DCholera
    Show answer & solution

    Correct answer: (A) Tuberculosis

    Tuberculosis, caused by Mycobacterium tuberculosis, spreads through droplets released in the air when an infected person coughs or sneezes, making it airborne. Malaria and dengue are vector-borne (mosquitoes) while cholera is water-borne, so none of these travel primarily through air.

23. Q23

    What are the four human blood types in ABO blood group typing?

    • AAO, BO, A and B
    • BA, B, AB and O
    • CA, AB, BO and O
    • DAB, AO, B and O
    Show answer & solution

    Correct answer: (B) A, B, AB and O

    In the ABO system the four blood groups are A, B, AB and O, determined by the presence or absence of A and B antigens on red cells. The other options invent non-existent labels like AO, BO or AB combinations that are not standard ABO phenotype names.

24. Q24

    Which one of the following is not a part of the male reproductive system in human beings?

    • AProstate gland
    • BTestis
    • CCervix
    • DScrotum
    Show answer & solution

    Correct answer: (C) Cervix

    The cervix is the lower part of the uterus and belongs to the female reproductive system, not the male. The prostate gland, testis and scrotum are all genuine components of the male reproductive system.

25. Q25

    Which of the following are the different parts of a human brain?

    • AForefront brain, Standard brain and Hind brain
    • BFore brain, Median brain and Rear brain
    • CFore brain, Mid brain and Hind brain
    • DPrecursor brain, Mean brain and Hind brain
    Show answer & solution

    Correct answer: (C) Fore brain, Mid brain and Hind brain

    The human brain is divided into three major parts: the fore brain (cerebrum, thalamus, hypothalamus), the mid brain, and the hind brain (cerebellum, pons, medulla). The other options use invented or mistranslated terms such as 'standard brain' or 'mean brain'.

26. Q26

    Tooth enamel of humans is made up of :

    • ACalcium phosphate
    • BSodium hydrogen carbonate
    • CSodium hydroxide
    • DLactic acid
    Show answer & solution

    Correct answer: (A) Calcium phosphate

    Tooth enamel, the hardest tissue in the body, is composed mainly of calcium phosphate in the form of hydroxyapatite crystals. Lactic acid produced by mouth bacteria actually erodes this enamel, and the sodium compounds listed are not structural constituents of teeth.

27. Q27

    The inner lining of the human small intestine has numerous finger-like projections called :

    • ASphincter
    • BVilli
    • CEnzymes
    • DPlaques
    Show answer & solution

    Correct answer: (B) Villi

    The finger-like projections lining the small intestine are called villi; they greatly increase the surface area for absorption of digested nutrients. A sphincter is a ring of muscle, enzymes are catalytic proteins, and plaques are unrelated deposits, so none of these describe the projections.

28. Q28

    Which of the following represent disaccharides?

    • AStarch and glycogen
    • BGlucose and galactose
    • CMaltose and lactose
    • DRibose and xylose
    Show answer & solution

    Correct answer: (C) Maltose and lactose

    Maltose (glucose+glucose) and lactose (glucose+galactose) are disaccharides made of two monosaccharide units. Starch and glycogen are polysaccharides; glucose and galactose are monosaccharides; and ribose and xylose are also single-sugar pentoses.

29. Q29

    Which one of the following organelles can be seen in a prokaryotic cell?

    • AMitochondria
    • BDefinitive nucleus
    • CRibosomes
    • DGolgi bodies
    Show answer & solution

    Correct answer: (C) Ribosomes

    Ribosomes are the only organelle in the list present in prokaryotic cells, where they carry out protein synthesis. Prokaryotes lack a membrane-bound (definitive) nucleus, mitochondria and Golgi bodies, all of which are features exclusive to eukaryotic cells.

30. Q30

    A solution with a pH value less than 7 is a/an :

    • ANeutral solution
    • BBasic solution
    • CAcidic solution
    • DHypotonic solution
    Show answer & solution

    Correct answer: (C) Acidic solution

    A pH value below 7 indicates an excess of hydrogen ions, defining an acidic solution. A pH of exactly 7 is neutral and above 7 is basic; 'hypotonic' refers to solute concentration and is unrelated to pH.

31. Q31

    Which language uses the symbolic representation of machine codes needed to program a particular processor or processor family ?

    • AMachine Language
    • BAssembly Language
    • CHigh-Level Language
    • DAll of the above
    Show answer & solution

    Correct answer: (B) Assembly Language

    Assembly language uses mnemonic symbolic representations (like MOV, ADD) of the binary machine codes specific to a particular processor or processor family, making programming more human-readable than raw machine language. Machine language is pure binary, while high-level languages are hardware-independent, so neither fits the description of 'symbolic representation of machine codes'.

32. Q32

    What are the uses of software ports ? 1. Connect client computer to server 2. Connect external devices to computer 3. Identify different services like email, file transfer 4. Connecting peripherals like cameras, scanners Select the answer using the code given below :

    • A1 and 2
    • B1 and 3
    • C2 and 3
    • D2 and 4
    Show answer & solution

    Correct answer: (B) 1 and 3

    Software (logical) ports are numeric identifiers that connect a client to a server and distinguish network services such as email (SMTP port 25), file transfer (FTP port 21), etc., so statements 1 and 3 are correct. Connecting external physical devices, peripherals like cameras and scanners refers to hardware ports (USB), not software ports, ruling out 2 and 4.

33. Q33

    Assuming the computer is a 4-bit computer, what result is produced after subtraction of 3 from 5 using the 2's complement representation ?

    • A0101
    • B10010
    • C1101
    • D11001
    Show answer & solution

    Correct answer: (B) 10010

    In 2's complement, 5 = 0101 and 3 = 0011; the 2's complement of 3 is 1101, so 5 - 3 = 0101 + 1101 = 10010, where the leading 1 is the discarded carry-out and the true 4-bit result 0010 equals decimal 2. The option showing the full 5-bit sum 10010 is the intended answer.

34. Q34

    Which one of the following is not a logical operator ?

    • ANOT
    • BOR
    • CAND
    • DDivision
    Show answer & solution

    Correct answer: (D) Division

    NOT, OR and AND are the fundamental logical (Boolean) operators used in logic and programming. Division is an arithmetic operator, not a logical one, so it is the odd one out.

35. Q35

    Which among the following are the purposes of deploying a Firewall? 1. Examine each packet arriving from Internet 2. Prevent unauthorised access 3. Block suspicious activity 4. Interconnect telephones Select the answer using the code given below:

    • A1 and 2 only
    • B1, 3 and 4
    • C2 and 3 only
    • D1, 2 and 3
    Show answer & solution

    Correct answer: (D) 1, 2 and 3

    A firewall examines each packet arriving from the Internet, prevents unauthorised access and blocks suspicious activity, so statements 1, 2 and 3 are its purposes. Interconnecting telephones is unrelated to firewalls, so statement 4 is excluded.

36. Q36

    Which of the following statements about India's military arsenal is/are correct? 1. HAMMER is a weapon system built for the Rafale fighter aircraft. 2. SCALP cruise missile is also known as Storm Shadow. 3. BrahMos missiles are built under a joint venture between India and Russia. Select the answer using the code given below :

    • A1 and 2 only
    • B2 and 3 only
    • C1, 2 and 3
    • D3 only
    Show answer & solution

    Correct answer: (C) 1, 2 and 3

    HAMMER is a precision air-to-ground weapon integrated on India's Rafale jets, the SCALP cruise missile is the French designation of the same weapon marketed as Storm Shadow, and BrahMos is an India-Russia (DRDO-NPOM) joint venture. All three statements are correct (C).

37. Q37

    Recently, ICAR (Indian Council of Agricultural Research) has developed the world's first genome-edited rice varieties. Which of the following statements is/are correct with respect to the developed products? 1. The genome-edited varieties – DRR Rice 100 (Kamla) and Pusa DST Rice 1 have been developed by ICAR-IARI, New Delhi. 2. DRR Rice 100 (Kamla), based on Samba Mahsuri, has a shorter duration of maturity. Select the answer using the code given below:

    • A1 only
    • B2 only
    • CBoth 1 and 2
    • DNeither 1 nor 2
    Show answer & solution

    Correct answer: (B) 2 only

    Statement 1 is wrong because DRR Rice 100 (Kamla) was developed by ICAR-IIRR (Hyderabad), while only Pusa DST Rice 1 came from ICAR-IARI, New Delhi. Statement 2 is correct: DRR Rice 100 (Kamla), derived from Samba Mahsuri, matures earlier (shorter duration), so B is right.