-by Pre Empower Oct 5 : Daily Quiz for Civil Services Prelims Examination
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Welcome to Pre Empower, your daily destination for mastering multiple-choice questions (MCQs) framed for Civil Services Examinations. Each day, we present a diverse set of carefully crafted MCQs to enhance your knowledge, boost your confidence, and prepare you for success in your civil services examinations of UPSC CSE and other State PCS like APSC, BPSC, UPPCS and others in the best possible manner.
Questions have been designed as per the demands of examination that cover a wide range of topics, including General Studies, Current Affairs, and Aptitude for CSAT. With Pre Empower, you’ll not only test your understanding but also develop critical thinking skills essential for tackling the challenges of the Preliminary exam in the best possible manner.
Join us at SMART IAS Foundation on this journey to achieve your goals and secure your future in Civil Services.
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Question 1 of 5
1. Question
A person standing near a fast-moving train feels a push towards the train. This phenomenon can be explained by:
(i) Bernoulli’s principle
(ii) Pascal’s law
(iii) Newton’s third law
Select the correct explanation using the codes given below:Correct
Answer: Option A
Explanation: This phenomenon can be explained using Bernoulli’s principle, which states that an increase in the speed of a fluid (in this case, air) occurs simultaneously with a decrease in pressure. When a train moves at high speed, the air velocity between the train and the person increases, which results in a decrease in air pressure in that region. On the other side, the pressure remains relatively higher, creating a net force that pushes the person towards the train. This is similar to the phenomenon where two parallel boats come closer when they move alongside each other at high speed.
Pascal’s law is not relevant here because it deals with the pressure exerted by a fluid in a confined space, which is transmitted equally in all directions. Newton’s third law refers to action-reaction pairs and does not explain the pressure difference caused by fluid motion in this context.Incorrect
Answer: Option A
Explanation: This phenomenon can be explained using Bernoulli’s principle, which states that an increase in the speed of a fluid (in this case, air) occurs simultaneously with a decrease in pressure. When a train moves at high speed, the air velocity between the train and the person increases, which results in a decrease in air pressure in that region. On the other side, the pressure remains relatively higher, creating a net force that pushes the person towards the train. This is similar to the phenomenon where two parallel boats come closer when they move alongside each other at high speed.
Pascal’s law is not relevant here because it deals with the pressure exerted by a fluid in a confined space, which is transmitted equally in all directions. Newton’s third law refers to action-reaction pairs and does not explain the pressure difference caused by fluid motion in this context. -
Question 2 of 5
2. Question
Which of the following statements regarding electric charge is correct?
(i) The SI unit of electric charge is Coulomb.
(ii) Electric charge can be positive or negative.
(iii) Charge is a vector quantity.
Select the correct statements using the codes given below:Correct
Answer: Option C
Explanation: The SI unit of electric charge is the Coulomb (C), named after Charles-Augustin de Coulomb, who discovered the inverse-square law of electrostatics. This makes statement (i) correct.
Electric charge can be either positive or negative, depending on whether it is associated with protons (positive) or electrons (negative). This duality of electric charge leads to the concepts of attraction and repulsion between charged particles, as described by Coulomb’s law, which makes statement (ii) correct.
Charge is a scalar quantity, which means it only has magnitude and no direction. Scalar quantities are distinguished from vector quantities, which have both magnitude and direction. Therefore, statement (iii) is incorrect. Charge does not have directionality, although electric field and electric force, which depend on the presence of a charge, are vector quantities.Incorrect
Answer: Option C
Explanation: The SI unit of electric charge is the Coulomb (C), named after Charles-Augustin de Coulomb, who discovered the inverse-square law of electrostatics. This makes statement (i) correct.
Electric charge can be either positive or negative, depending on whether it is associated with protons (positive) or electrons (negative). This duality of electric charge leads to the concepts of attraction and repulsion between charged particles, as described by Coulomb’s law, which makes statement (ii) correct.
Charge is a scalar quantity, which means it only has magnitude and no direction. Scalar quantities are distinguished from vector quantities, which have both magnitude and direction. Therefore, statement (iii) is incorrect. Charge does not have directionality, although electric field and electric force, which depend on the presence of a charge, are vector quantities. -
Question 3 of 5
3. Question
When a ray of light travels from one medium to another, its wavelength changes but its frequency remains the same because:
(i) Frequency depends on the source of light.
(ii) Wavelength depends on the speed of light in the medium.
(iii) Energy of the photon remains unchanged.
Select the correct reason/reasons using the codes given below:Correct
Answer: Option B
Explanation: When a light ray passes from one medium to another, such as from air to water, it experiences a phenomenon called refraction. During this process, the speed of light changes due to the difference in the optical density of the media. However, the frequency of light remains unchanged because the frequency is determined by the source of light and is intrinsic to the type of light emitted by the source.
The wavelength of light is directly proportional to its speed. When light enters a medium where its speed decreases (e.g., from air to water), the wavelength also decreases, but the frequency stays the same, ensuring the wave equation v=fλ (where v is speed, f is frequency, and λ is wavelength) holds true.
The energy of a photon is given by E= hf, where h is Planck’s constant, and f is the frequency. Since the frequency does not change, the photon’s energy also remains unchanged. This explanation, however, does not directly address why wavelength changes, so statement (iii) is not the primary reason here.Incorrect
Answer: Option B
Explanation: When a light ray passes from one medium to another, such as from air to water, it experiences a phenomenon called refraction. During this process, the speed of light changes due to the difference in the optical density of the media. However, the frequency of light remains unchanged because the frequency is determined by the source of light and is intrinsic to the type of light emitted by the source.
The wavelength of light is directly proportional to its speed. When light enters a medium where its speed decreases (e.g., from air to water), the wavelength also decreases, but the frequency stays the same, ensuring the wave equation v=fλ (where v is speed, f is frequency, and λ is wavelength) holds true.
The energy of a photon is given by E= hf, where h is Planck’s constant, and f is the frequency. Since the frequency does not change, the photon’s energy also remains unchanged. This explanation, however, does not directly address why wavelength changes, so statement (iii) is not the primary reason here. -
Question 4 of 5
4. Question
Which of the following best explains why a gas undergoes an adiabatic process?
(i) No heat is exchanged with the surroundings.
(ii) Temperature of the system remains constant.
(iii) The internal energy changes due to work done.Select the correct answer using the codes given below:
Correct
Answer: Option B
Explanation: In an adiabatic process, the system is perfectly insulated, meaning no heat is exchanged with the surroundings, making statement (i) correct. As a result, the system’s internal energy can only change due to the work done on or by the system. For a gas, internal energy is related to temperature, so when work is done by the gas (expansion), the internal energy decreases, leading to a temperature drop. Conversely, when work is done on the gas (compression), the internal energy increases, causing the temperature to rise, thus proving statement (iii) correct.
Statement (ii) is incorrect because, in an adiabatic process, the temperature does not necessarily remain constant. It changes as a consequence of changes in internal energy, which depends on the work done.Incorrect
Answer: Option B
Explanation: In an adiabatic process, the system is perfectly insulated, meaning no heat is exchanged with the surroundings, making statement (i) correct. As a result, the system’s internal energy can only change due to the work done on or by the system. For a gas, internal energy is related to temperature, so when work is done by the gas (expansion), the internal energy decreases, leading to a temperature drop. Conversely, when work is done on the gas (compression), the internal energy increases, causing the temperature to rise, thus proving statement (iii) correct.
Statement (ii) is incorrect because, in an adiabatic process, the temperature does not necessarily remain constant. It changes as a consequence of changes in internal energy, which depends on the work done. -
Question 5 of 5
5. Question
Which of the following statements about the particle nature of light is correct?
(i) It is demonstrated by the photoelectric effect.
(ii) It shows that light behaves as discrete packets called photons.
(iii) It supports the wave theory of light.
Select the correct statements using the codes given below:Correct
Answer: Option D
Explanation: The photoelectric effect demonstrates that light consists of discrete energy packets called photons. When light shines on the surface of certain metals, it ejects electrons, but this happens only if the light’s frequency exceeds a certain threshold. This behavior cannot be explained by the wave theory of light, which would predict that increasing the intensity should always result in electron emission, regardless of frequency. Instead, it confirms that light behaves as particles, as explained by Albert Einstein in 1905.
Statement (ii) is correct because it explains that the particle nature of light implies it is made up of photons, each with energy proportional to its frequency. Statement (iii) is incorrect because the photoelectric effect does not support the wave theory; rather, it is evidence for the quantum theory, which recognizes both particle and wave characteristics of light.Incorrect
Answer: Option D
Explanation: The photoelectric effect demonstrates that light consists of discrete energy packets called photons. When light shines on the surface of certain metals, it ejects electrons, but this happens only if the light’s frequency exceeds a certain threshold. This behavior cannot be explained by the wave theory of light, which would predict that increasing the intensity should always result in electron emission, regardless of frequency. Instead, it confirms that light behaves as particles, as explained by Albert Einstein in 1905.
Statement (ii) is correct because it explains that the particle nature of light implies it is made up of photons, each with energy proportional to its frequency. Statement (iii) is incorrect because the photoelectric effect does not support the wave theory; rather, it is evidence for the quantum theory, which recognizes both particle and wave characteristics of light.
