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All questions of Physics for UPSC CSE Exam

What type of current flows in only one direction and is produced by sources like batteries and solar cells?
  • a)
    Direct current (DC)
  • b)
    Alternating current (AC)
  • c)
    Magnetic current (MC)
  • d)
    Electric current (EC)
Correct answer is option 'A'. Can you explain this answer?

Lohit Matani answered
Direct current (DC) is the type of current that flows in only one direction. It is produced by sources such as batteries, solar cells, and dynamos. In DC, the electric charge moves steadily in a single direction.
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What is the term for the rise of a liquid inside a small-diameter tube due to adhesive forces between the liquid and the tube's inner walls?
  • a)
    Conduction
  • b)
    Convection
  • c)
    Capillary action
  • d)
    Surface tension
Correct answer is option 'C'. Can you explain this answer?

Ias Masters answered
Capillary action is the phenomenon where a liquid rises inside a small-diameter tube, such as a capillary, due to adhesive forces between the liquid and the inner walls of the tube. This effect is particularly noticeable in narrow tubes and is governed by a balance between cohesive and adhesive forces.

What is the property of a perfectly black body with regard to incoming radiation?
  • a)
    It reflects all incoming radiation.
  • b)
    It absorbs all incoming radiation.
  • c)
    It transmits all incoming radiation.
  • d)
    It scatters all incoming radiation.
Correct answer is option 'B'. Can you explain this answer?

Goel UPSC Coaching Center answered
A perfectly black body is a theoretical object that absorbs all incoming electromagnetic radiation without reflecting or transmitting any of it. It is often used as an idealized concept in thermodynamics and radiation physics to understand the behavior of real objects regarding emission and absorption of radiation.

What type of current periodically reverses direction and is used in most electrical power distribution systems?
  • a)
    Direct current (DC)
  • b)
    Alternating current (AC)
  • c)
    Magnetic current (MC)
  • d)
    Electric current (EC)
Correct answer is option 'B'. Can you explain this answer?

T.S Academy answered
Alternating current (AC) is the type of current that periodically reverses its direction of flow. It is commonly used in most electrical power distribution systems, making it possible to transmit electricity over long distances efficiently. AC is characterized by its sinusoidal waveform, and it is the standard for household electrical outlets.

What is the range of human hearing for sound frequencies?
  • a)
    20 Hz to 200 Hz
  • b)
    2 Hz to 20 Hz
  • c)
    20 Hz to 20,000 Hz
  • d)
    200 Hz to 2,000 Hz
Correct answer is option 'C'. Can you explain this answer?

Master Training Institute answered
The audible range of sound for human beings typically extends from approximately 20 Hz (hertz) to 20,000 Hz. Sounds with frequencies below 20 Hz are called infrasonic sound, while those with frequencies higher than 20,000 Hz are referred to as ultrasonic sound. Human hearing varies among individuals, but this is the typical range.

What is the fundamental quantity represented by the symbol "m" and is measured in kilograms (kg)?
  • a)
    Temperature
  • b)
    Mass
  • c)
    Electric current
  • d)
    Luminous intensity
Correct answer is option 'B'. Can you explain this answer?

K.L Institute answered
The fundamental quantity represented by the symbol "m" and measured in kilograms (kg) is mass. Mass is a measure of the amount of matter an object has, and it is one of the fundamental quantities of the International System of Units (SI).

Which of the following statements is true about the critical mass in a nuclear chain reaction?
  • a)
    Critical mass is the maximum mass of uranium needed for a nuclear chain reaction.
  • b)
    Critical mass is the minimum mass of uranium needed for a nuclear chain reaction.
  • c)
    Critical mass is always constant and does not vary with the type of fissile material.
  • d)
    Critical mass is the mass of uranium that remains unreacted in a nuclear chain reaction.
Correct answer is option 'B'. Can you explain this answer?

Capstone Ias Learning answered
Critical mass refers to the minimum mass of fissile material, such as uranium or plutonium, required to sustain a self-sustaining nuclear chain reaction. Below the critical mass, the reaction will not continue indefinitely, while above it, the reaction will continue and potentially lead to an explosion in the case of an uncontrolled chain reaction.

What type of wave exhibits particle motion that is parallel to the direction of energy transport?
  • a)
    Longitudinal wave
  • b)
    Transverse wave
  • c)
    Electromagnetic wave
  • d)
    Mechanical wave
Correct answer is option 'A'. Can you explain this answer?

Spectrum Coaching Institute answered
In a longitudinal wave, the motion of individual particles of the medium is parallel to the direction of energy transport. This means that the particles of the medium move back and forth in the same direction that the wave is traveling. Sound waves in air are a classic example of longitudinal waves, where air particles oscillate in the same direction as the sound wave is propagating.

What is the process of heat transfer that does not require a medium for propagation?
  • a)
    Conduction
  • b)
    Convection
  • c)
    Radiation
  • d)
    Expansion
Correct answer is option 'C'. Can you explain this answer?

Goel UPSC Coaching Center answered
Radiation is the process of heat transfer that does not require a medium for propagation. It involves the emission of electromagnetic waves, such as infrared radiation, from a hot object to its surroundings. Unlike conduction and convection, radiation can occur through a vacuum, making it essential for the transfer of heat from the Sun to the Earth.

What type of waves are sound waves in air, where particles of the medium vibrate parallel to the direction of the wave's movement?
  • a)
    Longitudinal waves
  • b)
    Transverse waves
  • c)
    Electromagnetic waves
  • d)
    Surface waves
Correct answer is option 'A'. Can you explain this answer?

Academic Studio answered
Sound waves in air are classified as longitudinal waves. In a longitudinal wave, the particles of the medium (in this case, air) vibrate parallel to the direction in which the wave is moving. This means that as sound waves propagate through the air, the air particles oscillate back and forth in the same direction as the wave's movement.

What is the SI unit for measuring an electric current?
  • a)
    Coulomb (C)
  • b)
    Watt (W)
  • c)
    Ampere (A)
  • d)
    Volt (V)
Correct answer is option 'C'. Can you explain this answer?

EduRev UPSC answered
The SI unit for measuring an electric current is the ampere (A). An ampere is defined as the flow of electric charge through a surface at the rate of one coulomb per second. It is used to measure the strength of an electric current in a circuit.

What phenomenon occurs when a changing magnetic field induces an electromotive force (EMF) in a conductor, causing electric current to flow?
  • a)
    Ohm's Law
  • b)
    Ampere's Law
  • c)
    Faraday's Law of Electromagnetic Induction
  • d)
    Coulomb's Law
Correct answer is option 'C'. Can you explain this answer?

K.L Institute answered
Faraday's Law of Electromagnetic Induction states that a changing magnetic field induces an electromotive force (EMF) in a conductor, which in turn causes electric current to flow in a closed circuit. This phenomenon is the basis for the generation of electricity in generators.

What force opposes the relative motion of solid surfaces and is responsible for resisting the motion of objects against each other?
  • a)
    Magnetic force
  • b)
    Frictional force
  • c)
    Gravitational force
  • d)
    Tension force
Correct answer is option 'B'. Can you explain this answer?

Upsc Toppers answered
The force that opposes the relative motion of solid surfaces and is responsible for resisting the motion of objects against each other is called the frictional force. It acts in the direction opposite to the direction of motion and is a common force in everyday life.

What is the name of the law that states that every two objects in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them?
  • a)
    Coulomb's Law
  • b)
    Ampere's Law
  • c)
    Newton's Universal Law of Gravitation
  • d)
    Ohm's Law
Correct answer is option 'C'. Can you explain this answer?

T.S Academy answered
Newton's Universal Law of Gravitation states that every two objects in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This law describes the gravitational attraction between objects and is fundamental to our understanding of celestial motion.

What does the Law of Conservation of Energy state?
  • a)
    Energy can be created but not destroyed.
  • b)
    Energy can be destroyed but not created.
  • c)
    The total energy in a closed system remains constant; it can neither be created nor destroyed.
  • d)
    Energy is always lost in any physical process.
Correct answer is option 'C'. Can you explain this answer?

Academic Studio answered
The Law of Conservation of Energy states that in a closed system, the total energy remains constant over time. Energy can neither be created nor destroyed; it can only change forms or be transferred between different parts of the system.

Which fundamental quantity is represented by the symbol "K" and is measured in Kelvin (K)?
  • a)
    Electric current
  • b)
    Mass
  • c)
    Temperature
  • d)
    Luminous intensity
Correct answer is option 'C'. Can you explain this answer?

K.L Institute answered
The fundamental quantity represented by the symbol "K" and measured in Kelvin (K) is temperature. Kelvin is the SI unit of temperature, and it is exactly 1/273.16 of the thermodynamic temperature of the triple point of water.

What is the temperature at which all molecular motion theoretically ceases, known as?
  • a)
    Absolute zero
  • b)
    Melting point
  • c)
    Boiling point
  • d)
    Room temperature
Correct answer is option 'A'. Can you explain this answer?

Ias Masters answered
Absolute zero is the lowest possible temperature where all molecular motion theoretically ceases. It is typically defined as 0 Kelvin (0 K) on the Kelvin scale or -273.15 degrees Celsius (-273.15°C) on the Celsius scale. At absolute zero, particles have the minimum possible energy and exhibit no thermal motion.

What is the phenomenon called when there is an apparent upward shift in frequency for an observer and a source approaching each other?
  • a)
    Refraction
  • b)
    Diffraction
  • c)
    Doppler effect
  • d)
    Interference
Correct answer is option 'C'. Can you explain this answer?

Master Training Institute answered
The Doppler effect is the phenomenon produced by a moving source of waves, in which there is an apparent shift in frequency when the source and the observer are approaching each other. This effect is observed with various types of waves, including sound waves, where it causes a change in pitch as a sound source moves relative to an observer.

Which law of thermodynamics states that energy can be changed from one form to another but cannot be created or destroyed?
  • a)
    Zeroth Law of Thermodynamics
  • b)
    First Law of Thermodynamics
  • c)
    Second Law of Thermodynamics
  • d)
    Third Law of Thermodynamics
Correct answer is option 'B'. Can you explain this answer?

EduRev UPSC answered
The First Law of Thermodynamics, also known as the law of energy conservation, states that energy can be changed from one form to another, but it cannot be created or destroyed. In other words, the total energy within a closed system remains constant.

Chapter doubts & questions for Physics - General Science(Prelims) by IRS Divey Sethi 2025 is part of UPSC CSE exam preparation. The chapters have been prepared according to the UPSC CSE exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for UPSC CSE 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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