UPSC CISF-AC-EXE

11. An acid solution of pH equal to three is gradually diluted with water.

An acid solution of pH equal to three is gradually diluted with water. As a result of this dilution, the pH of the solution will

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reach near to zero.
reach near to fourteen.
reach near to seven.
remain unchanged.
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An acid solution with pH = 3 has a relatively high concentration of H+ ions. Diluting this solution with pure water (which has a neutral pH of 7) reduces the concentration of the acid, and thus the concentration of H+ ions from the acid. The total concentration of H+ ions approaches the concentration of H+ ions in pure water (which is $10^{-7}$ M at 25°C, corresponding to pH 7). As the concentration of H+ decreases, the pH value (which is -log[H+]) increases. The pH will move from 3 towards 7, but it will not exceed 7 when diluting with pure water.
Diluting an acidic solution with neutral water increases its pH, moving it towards 7.
Similarly, diluting a basic solution with neutral water decreases its pH, moving it towards 7. The pH of a solution being diluted with pure water will approach the pH of pure water (7), but will not cross the neutrality point unless the original solution was extremely concentrated or involved complex acid-base equilibria not typical for this type of question.

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12. Consider the following statement : “When a body is in equilibrium, the

Consider the following statement :
“When a body is in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point.”
Which one of the following laws is described in the above statement ?

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Law of motion
Law of moments
Law of momentum
Law of magnetism
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The statement “When a body is in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point” is the definition of rotational equilibrium. This condition is formally known as the Law of Moments, which is part of the requirements for a body to be in complete equilibrium (the other part being translational equilibrium, i.e., zero net force).
The Law of Moments is the principle that governs rotational equilibrium.
Moment (or torque) is the tendency of a force to cause rotation around an axis or pivot point. For a body to be in complete mechanical equilibrium, both the net force and the net moment acting on it must be zero.

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13. Which of the following statements regarding temperature of an object i

Which of the following statements regarding temperature of an object in Kelvin scale is/are correct ?

  • 1. It can be a negative, zero or positive quantity.
  • 2. It can either be a negative or a positive quantity.
  • 3. It can never be negative.
  • 4. It can be a positive definite quantity.

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1 and 2 only
2 and 4 only
3 and 4 only
4 only
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The Kelvin scale is an absolute temperature scale. The zero point (0 K) is absolute zero, the theoretical lowest possible temperature. Temperatures on the Kelvin scale are always non-negative (greater than or equal to zero).
Statement 1: Incorrect, as Kelvin temperature cannot be negative.
Statement 2: Incorrect, as Kelvin temperature cannot be negative and can be zero.
Statement 3: Correct, Kelvin temperature can never be negative (it is always $\ge 0$).
Statement 4: Interpreting “positive definite quantity” in this context to mean a quantity that is positive or zero (non-negative), this statement is correct, as Kelvin temperature is always $\ge 0$. If interpreted strictly as strictly positive (> 0), it would be incorrect as 0 K is possible. Given the options, the non-negative interpretation is most likely intended for statement 4, making both 3 and 4 correct.
Temperature on the Kelvin scale is always non-negative ($\ge 0$).
Absolute zero (0 K or -273.15 °C) is the point at which particles have minimum possible motion (though not zero motion according to quantum mechanics). The Kelvin scale is used extensively in scientific applications.

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14. Which one of the following statements about the Principle of Calorimet

Which one of the following statements about the Principle of Calorimetry is correct ?

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It is always valid.
It is valid when temperature is constant.
It is valid only when there is no change of state.
It is valid only under equilibrium condition.
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The Principle of Calorimetry is based on the law of conservation of energy. It states that in an isolated system, the total amount of heat lost by the hot bodies is equal to the total amount of heat gained by the cold bodies. This principle is fundamentally valid whenever heat exchange occurs in an isolated system, including processes involving changes of state (by accounting for latent heat) and processes involving temperature changes. Options B, C, and D state conditions under which the principle is *only* valid, which are incorrect limitations. The principle is valid even when temperature is not constant (during temperature change), when there is a change of state (by including latent heat), and it describes the process of heat exchange *towards* equilibrium, not only at equilibrium. Therefore, “It is always valid” (interpreted as valid in an isolated system for which it is defined) is the most accurate statement among the choices, as the other options describe false limitations.
The Principle of Calorimetry is based on energy conservation in thermal interactions and applies in isolated systems, irrespective of whether temperature changes or phase changes occur.
In practical calorimetry experiments, efforts are made to create an isolated system to minimize heat exchange with the surroundings and ensure the principle holds true for the components within the calorimeter.

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15. Which one of the following determines the direction of induced current

Which one of the following determines the direction of induced current ?

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Fleming's left hand rule
Fleming's right hand rule
Feynman's left hand rule
Right hand thumb rule
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Fleming’s Right-Hand Rule is used to determine the direction of the induced electric current in a conductor when it is moved in a magnetic field or when the magnetic field around it changes. The thumb, forefinger, and middle finger are held mutually perpendicular: the thumb points in the direction of motion of the conductor, the forefinger points in the direction of the magnetic field, and the middle finger points in the direction of the induced current.
Fleming’s Right-Hand Rule determines the direction of induced current, while Fleming’s Left-Hand Rule determines the direction of force on a current-carrying conductor in a magnetic field.
The phenomenon of induced current is described by Faraday’s Law of electromagnetic induction, and its direction is governed by Lenz’s Law, which is encapsulated by Fleming’s Right-Hand Rule.

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16. Which of the following statements about a body under equilibrium is/ar

Which of the following statements about a body under equilibrium is/are correct ?

  • 1. No forces are acting.
  • 2. A number of parallel forces may be acting.
  • 3. The law of moments must apply.

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1, 2 and 3
2 and 3 only
1 and 3 only
2 only
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A body is under equilibrium if the net force acting on it is zero (translational equilibrium) and the net torque acting on it is zero (rotational equilibrium).
Statement 1: “No forces are acting” is incorrect. Forces can be acting, but they must be balanced, meaning the vector sum of all forces is zero.
Statement 2: “A number of parallel forces may be acting” is correct. For example, if two equal and opposite parallel forces act on a body, they form a couple, which produces a torque. For the body to be in equilibrium, this torque must be balanced by other torques, and the net force must be zero (which these two forces satisfy). More generally, parallel forces can sum to zero net force and zero net torque.
Statement 3: “The law of moments must apply” is correct. The Law of Moments states that for rotational equilibrium, the sum of clockwise moments about any point equals the sum of anticlockwise moments about the same point. This is a necessary condition for a body to be in equilibrium.
Equilibrium requires zero net force and zero net torque. The Law of Moments describes the condition for zero net torque.
A body in equilibrium can be either at rest (static equilibrium) or moving with constant velocity (dynamic equilibrium). Both require the net force and net torque to be zero.

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17. The X-chromosome linked colour blindness affects the ability to detect

The X-chromosome linked colour blindness affects the ability to detect the difference between which of the following lights ?

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Green light and red light
Yellow light and blue light
Blue light and violet light
Yellow light and red light
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X-chromosome linked colour blindness is most commonly red-green colour blindness. This condition affects the photoreceptor cells in the eye (cones) that are sensitive to red and green light, making it difficult to distinguish between these colours.
X-linked colour blindness primarily impairs the ability to distinguish between red and green colours.
Colour blindness is often inherited and is much more prevalent in males because the genes responsible for the most common forms are located on the X chromosome. Females have two X chromosomes, so a functional gene on one X chromosome can often compensate for a non-functional one on the other, whereas males only have one X chromosome.

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18. Young children with vitamin D deficiency have trouble in absorbing whi

Young children with vitamin D deficiency have trouble in absorbing which of the following minerals ?

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Calcium and Phosphorus
Iron and Sodium
Sodium and Potassium
Zinc and Iron
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Young children with vitamin D deficiency have trouble in absorbing Calcium and Phosphorus.
– Vitamin D is essential for the absorption of calcium and phosphorus from the small intestine.
– These minerals are crucial for bone mineralization and overall bone health.
– In children, a deficiency in vitamin D leads to inadequate absorption of calcium and phosphorus, resulting in rickets, a condition characterized by soft and weak bones, bone deformities, and impaired growth.
– Iron is essential for red blood cell formation, and its absorption is primarily influenced by factors like Vitamin C.
– Sodium and Potassium are important electrolytes, and their balance is regulated by the kidneys and other hormones, not directly by Vitamin D absorption.
– Zinc is involved in various metabolic processes, and its absorption is not directly dependent on Vitamin D.
Vitamin D is synthesized in the skin upon exposure to sunlight and can also be obtained from certain foods or supplements. Severe vitamin D deficiency can lead to osteomalacia in adults (softening of bones).

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19. In dialysis for kidney failure patients, the dialysing fluid is iso-os

In dialysis for kidney failure patients, the dialysing fluid is iso-osmotic to

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Blood
Urine
Water
Body fluid
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In dialysis for kidney failure patients, the dialysing fluid is iso-osmotic to Blood.
– Dialysis is a process that filters waste products and excess fluid from the blood when the kidneys are unable to perform these functions.
– The dialysing fluid, or dialysate, is a sterile solution that is separated from the patient’s blood by a semi-permeable membrane (the dialyser or peritoneum).
– The dialysate is carefully formulated to have an osmotic pressure similar to that of normal blood plasma (making it iso-osmotic to blood) to prevent damage to blood cells and large shifts in fluid balance.
– Waste products like urea and creatinine, which are in high concentration in the patient’s blood, diffuse across the membrane into the dialysate where their concentration is low.
– Excess electrolytes in the blood can also be removed, and necessary electrolytes added to the blood from the dialysate, facilitating balance.
– Water removal (ultrafiltration) is typically achieved by creating a pressure gradient or sometimes by adding glucose to the dialysate to increase its osmotic pressure slightly compared to blood, but the base solution is iso-osmotic.
While the dialysate composition aims to restore the body’s overall fluid and electrolyte balance (related to “Body fluid”), the direct interaction is with the blood flowing through the dialyser. Therefore, its osmotic property is most critically matched to blood plasma to ensure safe and effective filtration and solute exchange without causing harm to blood cells.

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20. Binomial nomenclature means

Binomial nomenclature means

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Biological names are generally in Latin and written in italics. The first word is the genus and the second word is the species.
Biological names are generally taken from father and mother.
Biological name originates from order and genus.
Biological name originates from phylum and genus.
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Binomial nomenclature means Biological names are generally in Latin and written in italics. The first word is the genus and the second word is the species.
– Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages.
– The first part of the name is the genus name, and the second part is the specific epithet (often called the species name).
– The genus name is always capitalized, and the specific epithet is not.
– Both parts are italicized when printed (e.g., Homo sapiens) or underlined when handwritten.
– This system was largely standardized by Carl Linnaeus in the 18th century.
– Options B, C, and D describe incorrect origins or structures for biological names.
Binomial nomenclature provides a unique and internationally recognized name for each species, avoiding confusion caused by common names which can vary regionally or for the same organism. This standardized naming system is fundamental to biological classification (taxonomy).

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