UPSC Geoscientist Archives

41. Which one of the following statements is correct regarding the magneti

Which one of the following statements is correct regarding the magnetic field inside a current carrying solenoid?

The magnetic field inside the solenoid is zero

The magnetic field inside the solenoid is uniform at all the points

The magnetic field inside the solenoid increases as we move towards the ends

The magnetic field inside the solenoid decreases as we move towards the ends

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The correct statement is that the magnetic field inside a current carrying solenoid is uniform at all points (for a sufficiently long solenoid). Option B is correct because, in the ideal case of an infinitely long solenoid, the magnetic field inside is perfectly uniform and parallel to the axis. For a real, long solenoid, this uniformity is a very good approximation over most of the interior volume, except near the ends.

For an ideal, infinitely long solenoid, the magnetic field inside is uniform and given by the formula B = μ₀ * n * I, where μ₀ is the permeability of free space, n is the number of turns per unit length, and I is the current. This formula shows the field is constant everywhere inside, independent of the position.

Outside a long solenoid, the magnetic field is nearly zero. Near the ends of a real solenoid, the magnetic field lines spread out, causing the field to become non-uniform and weaker than in the central region. However, in typical questions comparing the field at different points inside, the ideal case (uniform field) or the relative behavior (field strongest in the middle, weaker near ends) is considered. Option B represents the key characteristic of the internal field of a long solenoid.

42. A straight conducting wire carries a DC current through it. Which one

A straight conducting wire carries a DC current through it. Which one of the following statements is true regarding the magnetic field around the wire?

The magnetic field does not depend upon the amount of current flowing through the wire

The magnetic field does not depend upon the distance from the wire

The magnetic field depends upon the material of the wire

The magnetic field decreases with an increase from the wire

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The magnetic field around a straight conducting wire carrying a DC current decreases with an increase in distance from the wire.

The magnitude of the magnetic field (B) at a distance ‘r’ from a long, straight wire carrying a current ‘I’ is given by the formula $B = \frac{\mu_0 I}{2\pi r}$ (in vacuum or air). This formula shows that B is directly proportional to the current I and inversely proportional to the distance r.

According to the formula, the magnetic field strength decreases as the distance from the wire increases (option D). The magnetic field strength depends on the current flowing through the wire (option A is false). The magnetic field strength depends on the distance from the wire (option B is false). The formula contains $\mu_0$, the permeability of free space, which is a property of the medium, not the wire material itself (assuming the wire is non-magnetic and the medium is uniform) (option C is false). The direction of the magnetic field lines around the wire is circular, concentric with the wire, and can be determined by the right-hand rule.

43. Which one of the following is NOT a unit of magnetic field strength?

Which one of the following is NOT a unit of magnetic field strength?

Tesla

Gauss

Ampere - metre

Ampere/metre

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Ampere – metre (A·m) is NOT a unit of magnetic field strength.

Magnetic field strength can refer to magnetic flux density (B), measured in Tesla (T) or Gauss (G), or magnetic field intensity (H), measured in Amperes per metre (A/m). Ampere – metre (A·m) is the unit for magnetic dipole moment.

Tesla (T) is the SI unit for magnetic flux density (B). Gauss (G) is the CGS unit for magnetic flux density (1 T = 10^4 G). Ampere/metre (A/m) is the SI unit for magnetic field intensity (H). Magnetic field strength (H) and magnetic flux density (B) are related by the magnetic permeability of the medium ($B = \mu H$). Magnetic dipole moment (m) is a measure of the magnetic strength and orientation of a magnet or magnetic source.

44. Which one of the following is correct with regards to animals with bil

Which one of the following is correct with regards to animals with bilateral symmetry, triploblastic body and true body cavity?

Roundworm, earthworm and leech

Earthworm, leech and nereis

Ascaris, round worm and earthworm

Earthworm, sea cucumber and sea urchin

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Option B lists animals with bilateral symmetry, triploblastic body, and a true body cavity (coelom).

Animals that are bilaterally symmetrical and triploblastic are typically found from Platyhelminthes onwards. A true coelom (body cavity lined by mesoderm) is present in annelids, molluscs, arthropods, echinoderms (larvae, adults secondarily radial), and chordates. Earthworms, leeches, and nereis are all annelids. Annelids are characterized by bilateral symmetry, a triploblastic body plan, and a true coelom (eucoelomate).

Roundworms (Nematodes, e.g., Ascaris) are bilaterally symmetrical and triploblastic, but they possess a pseudocoelom, not a true coelom. Sea cucumbers and sea urchins belong to Echinodermata, which, while triploblastic coelomates, exhibit radial symmetry in their adult stage (their larvae are bilateral). Therefore, the animals listed in option B (Earthworm, leech, nereis – all annelids) fit all three criteria.

45. Which one of the following provides buoyancy to aquatic plants to help

Which one of the following provides buoyancy to aquatic plants to help them float?

Aerenchyma

Tracheid

Guard cell

Sclerenchyma

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Aerenchyma provides buoyancy to aquatic plants.

Aerenchyma is a modified parenchyma tissue found in many aquatic and wetland plants. It contains large air spaces (lacunae) that provide buoyancy, allowing the plant to float on the water surface. These air spaces also facilitate gas exchange (oxygen and carbon dioxide) to submerged tissues.

Tracheids are components of xylem involved in water transport and support. Guard cells surround stomata and regulate gas exchange but are not involved in buoyancy. Sclerenchyma provides mechanical support and strength due to its thick, lignified cell walls. Only aerenchyma is specifically adapted for providing buoyancy through its air-filled cavities.

46. Which one of the following is the correct sequence of parts in human a

Which one of the following is the correct sequence of parts in human alimentary canal?

Buccal cavity, oesophagus, stomach, small intestine, large intestine and anus

Buccal cavity, oesophagus, stomach, large intestine, small intestine and anus

Buccal cavity, stomach, oesophagus, small intestine, large intestine and anus

Buccal cavity, stomach, oesophagus, large intestine, small intestine and anus

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Option A represents the correct sequence of parts in the human alimentary canal.

Food enters the human digestive system through the mouth (buccal cavity), then passes down the pharynx and oesophagus to the stomach. From the stomach, it moves into the small intestine, then the large intestine, and finally indigestible material is eliminated through the anus. This represents a unidirectional flow.

The alimentary canal is a continuous tube extending from the mouth to the anus. The small intestine is where most digestion and absorption occur, and it is located between the stomach and the large intestine. The large intestine primarily absorbs water and electrolytes and forms faeces before excretion. The sequence in option A accurately reflects this anatomical pathway.

47. Which one of the following represents the correct hierarchical sequenc

Which one of the following represents the correct hierarchical sequence of taxonomic categories in ascending order?

Species $ ightarrow$ Genus $ ightarrow$ Order $ ightarrow$ Family $ ightarrow$ Class

Genus $ ightarrow$ Species $ ightarrow$ Order $ ightarrow$ Family $ ightarrow$ Class

Species $ ightarrow$ Genus $ ightarrow$ Family $ ightarrow$ Order $ ightarrow$ Class

Species $ ightarrow$ Genus $ ightarrow$ Order $ ightarrow$ Family $ ightarrow$ Class

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Option C represents the correct hierarchical sequence of taxonomic categories in ascending order.

The standard taxonomic hierarchy, from the lowest rank to the highest, is: Species $\rightarrow$ Genus $\rightarrow$ Family $\rightarrow$ Order $\rightarrow$ Class $\rightarrow$ Phylum $\rightarrow$ Kingdom $\rightarrow$ Domain. Ascending order means moving from lower to higher ranks.

Each rank in the hierarchy is a taxon. A species is a group of organisms that can interbreed and produce fertile offspring. Similar species are grouped into a genus. Similar genera are grouped into a family, and so on. This hierarchical system helps in classifying and organizing the diversity of life. Option C correctly places Family before Order, and Order before Class. Options A and D incorrectly place Order before Family. Option B starts with Genus, which is not the lowest rank listed.

48. Which of the following organisms are included in Kingdom Protista as g

Which of the following organisms are included in Kingdom Protista as given by R Whittakar?

Nostoc, mycoplasma and protozoans

Bacteria, amoeba and protozoan

Anabaena, bacteria and paramecium

Unicellular algae, diatoms, slime moulds and protozoans

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Option D lists organisms that are included in Kingdom Protista according to R.H. Whittaker’s five-kingdom classification.

R.H. Whittaker’s classification (1969) proposed five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. Kingdom Protista includes all single-celled eukaryotes. This encompasses a diverse group including unicellular algae (like Euglena), diatoms, slime moulds (which are often multicellular at certain stages but are considered protists), and protozoans (like Amoeba, Paramecium).

Options A, B, and C include organisms belonging to Kingdom Monera (Nostoc, mycoplasma, bacteria, Anabaena) which consists of prokaryotes (bacteria and cyanobacteria). Protozoans, unicellular algae, diatoms, and slime moulds are all eukaryotic and predominantly unicellular, fitting the description of Protista.

49. Cells of which one of the following tissues in animals undergo contrac

Cells of which one of the following tissues in animals undergo contraction and relaxation?

Muscular tissue

Connective tissue

Epithelial tissue

Nervous tissue

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Muscular tissue is the tissue in animals that undergoes contraction and relaxation.

Muscle cells ( myocytes or muscle fibers) contain specialized proteins, primarily actin and myosin, that interact to cause the cell to shorten (contract) and then return to its original length (relax). This ability is fundamental to movement in animals.

There are three types of muscular tissue: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is responsible for voluntary movements, smooth muscle for involuntary movements in internal organs (like digestion and blood flow), and cardiac muscle is responsible for the pumping action of the heart. Connective tissue provides support, binds tissues together, and transports substances. Epithelial tissue covers body surfaces and lines cavities. Nervous tissue transmits electrical and chemical signals.

50. Squamous epithelial cells are NOT found in:

Squamous epithelial cells are NOT found in:

lining of the mouth.

oesophagus.

skin.

kidney tubules.

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Squamous epithelial cells are NOT typically found as the primary lining in kidney tubules.

Squamous epithelium consists of flattened, thin cells, often forming smooth, protective, or permeable linings. While stratified squamous epithelium forms protective layers in the mouth, oesophagus, and skin, kidney tubules are primarily lined by cuboidal or columnar epithelium, which are more involved in secretion and absorption. A portion of the loop of Henle in the kidney is lined by thin squamous cells, but the general lining of the tubules is not squamous.

Simple squamous epithelium is found in the lining of blood vessels (endothelium), air sacs of lungs (alveoli), and lining of body cavities (mesothelium). Stratified squamous epithelium provides protection against abrasion and is found in the epidermis of the skin, lining of the mouth cavity, oesophagus, and vagina. Cuboidal epithelium is found in kidney tubules, ducts of glands, etc., and columnar epithelium is found in the lining of the stomach and intestines.