Physics MCQs

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Physics MCQs

Practice the latest Physics MCQs with answers and detailed explanations. This section includes chapter-wise multiple-choice questions covering mechanics, motion, force, work and energy, heat, light, electricity, magnetism, modern physics, waves, optics, and other important topics. These exam-oriented MCQs are ideal for Class 9–12, NEET, JEE, CUET, SSC, Banking, Railway, JKSSB, Defence, Police, and other competitive exams.

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Question #141
A particle performs Simple Harmonic Motion (SHM). If its displacement from the mean position is half of its amplitude, the ratio of its kinetic energy to potential energy is:
A. 1:1
B. 3:1
C. 1:3
D. 2:1
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Correct Answer: Option B

Explanation:
In SHM, Total Energy (E) = 1/2 k A^2. Potential Energy (U) at displacement x is 1/2 k x^2. Kinetic Energy (K) is E - U = 1/2 k (A^2 - x^2). Given x = A/2. U = 1/2 k (A/2)^2 = 1/2 k (A^2 / 4) = E/4. Since total energy is conserved, K = E - E/4 = 3E/4. The ratio of Kinetic to Potential Energy (K:U) is (3E/4) / (E/4) = 3:1.
This question belongs to: Science Physics
Question #142
Assertion (A): It is easier to pull a lawn roller than to push it. Reason (R): Pushing increases the apparent weight of the roller, thereby increasing the frictional force.
A. Both A and R are true but R is NOT the correct explanation of A.
B. Both A and R are true and R is the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Discuss
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Correct Answer: Option B

Explanation:
When you pull a roller at an upward angle, the vertical component of the applied force acts strictly upwards, reducing the normal reaction (N = mg - Fsin_theta) and thus reducing friction (muN). When you push it at a downward angle, the vertical component adds to the weight (N = mg + Fsin_theta), increasing the normal reaction and consequently increasing the rolling friction.
This question belongs to: Science Physics
Question #143
The time period of a simple pendulum on the surface of the moon compared to its time period on Earth is:
A. Decreased
B. Zero
C. Increased
D. The same
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Correct Answer: Option C

Explanation:
The time period of a pendulum is T = 2 * pi * sqrt(L/g). The acceleration due to gravity on the moon (g_moon) is roughly 1/6th of that on Earth (g_earth). Since g decreases, and T is strictly inversely proportional to the square root of g, the time period T must increase. The pendulum will swing much slower.
This question belongs to: Science Physics
Question #144
Which of the following physical quantities is completely conserved during an inelastic collision?
A. Linear momentum
B. Kinetic energy
C. Velocity
D. Mechanical energy
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Correct Answer: Option A

Explanation:
The fundamental law of conservation of momentum dictates that in a closed system with no external net forces, total linear momentum is always conserved regardless of the collision type. In an inelastic collision, some kinetic energy is converted into other forms of energy (like heat or sound or deformation work), meaning kinetic and total mechanical energy are explicitly NOT conserved.
This question belongs to: Science Physics
Question #145
According to the principle of homogeneity of dimensions, in an equation A = B + C, what must be true about the dimensions of A, B, and C?
A. A, B, and C must all have identical dimensions.
B. B and C must be dimensionless.
C. A must be dimensionless.
D. A must equal B times C.
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Correct Answer: Option A

Explanation:
The principle of homogeneity states that you can only add or subtract physical quantities that have the exact same dimensional formula (you can't add mass to length). Therefore, in the equation A = B + C, the terms B and C must have the same dimensions, and their sum will yield a quantity A that also shares those exact same dimensions.
This question belongs to: Science Physics
Question #146
A block of mass 10 kg is accelerating at 2 m/s^2 on a horizontal surface under an applied force of 50 N. What is the magnitude of the frictional force opposing its motion?
A. 20 N
B. 70 N
C. 50 N
D. 30 N
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Correct Answer: Option D

Explanation:
According to Newton's Second Law, the net force on the block is F_net = mass * acceleration = 10 kg * 2 m/s^2 = 20 N. The net force is the difference between the applied forward force and the opposing frictional force (F_net = F_applied - F_friction). So, 20 N = 50 N - F_friction. Solving for friction gives F_friction = 50 - 20 = 30 N.
This question belongs to: Science Physics
Question #147
What is the equivalent capacitance when three capacitors of 3 microfarads each are connected in series?
A. 0.33 microfarads
B. 3 microfarads
C. 9 microfarads
D. 1 microfarad
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Correct Answer: Option D

Explanation:
The formula for capacitors in series is exactly the opposite of resistors. 1/C_eq = 1/C1 + 1/C2 + 1/C3. Here, all are 3 uF. So, 1/C_eq = 1/3 + 1/3 + 1/3 = 3/3 = 1. Therefore, C_eq = 1 microfarad. When identical capacitors are in series, you simply divide the capacitance by the number of capacitors (3/3 = 1).
This question belongs to: Science Physics
Question #148
The specific resistance (resistivity) of a metallic conductor depends exclusively upon its:
A. Length
B. Nature of material and temperature
C. Cross-sectional area
D. Volume
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Correct Answer: Option B

Explanation:
Resistance depends on length and area (R = rho * L / A), but specific resistance or resistivity (rho) is an intrinsic property of the material itself. It does not depend on the geometric dimensions of the conductor (length, area, volume). Resistivity strictly depends on the atomic structure (nature of the material) and the thermal vibrations (temperature of the material).
This question belongs to: Science Physics
Question #149
Identify the logic gate that gives a HIGH (1) output only when both of its inputs are HIGH (1).
A. NOR gate
B. OR gate
C. NAND gate
D. AND gate
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Correct Answer: Option D

Explanation:
Logic gates process digital signals. An AND gate acts like two switches in series. Current (a logic HIGH or 1) will only flow to the output if Switch A AND Switch B are closed (HIGH). The truth table for an AND gate shows output = 1 solely when Input A = 1 and Input B = 1. In all other combinations, the output is strictly 0.
This question belongs to: Science Physics
Question #150
In a p-type semiconductor, the majority charge carriers and the minority charge carriers are respectively:
A. Holes and Electrons
B. Electrons and Holes
C. Protons and Electrons
D. Ions and Holes
Discuss
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Correct Answer: Option A

Explanation:
A p-type semiconductor is created by doping a pure semiconductor (like Silicon) with a trivalent impurity (like Boron). This creates a deficiency of one electron, creating a 'hole'. These positive holes vastly outnumber the thermally generated free electrons. Thus, holes are the majority charge carriers, and electrons are the minority charge carriers.
This question belongs to: Science Physics
Question #151
What is the physical meaning of the 'Work Function' of a metal in the context of the photoelectric effect?
A. The maximum kinetic energy of an emitted electron.
B. The minimum energy required to eject an electron from the metal surface.
C. The electrical resistance of the metal when light shines on it.
D. The total energy of an incident photon.
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Correct Answer: Option B

Explanation:
In Einstein's photoelectric theory, electrons are bound to the metal lattice. The 'work function' (often denoted by Phi or W) is defined strictly as the absolute minimum thermodynamic work (energy) needed to overcome these binding forces and remove an electron from the surface into a vacuum. If incident photon energy (hf) is less than the work function, absolutely no emission occurs.
This question belongs to: Science Physics
Question #152
A tuning fork produces 4 beats per second when sounded with a 256 Hz standard fork. When a little wax is attached to the tuning fork, the beat frequency drops to 2 beats per second. The original frequency of the tuning fork was:
A. 252 Hz
B. 254 Hz
C. 258 Hz
D. 260 Hz
Discuss
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Correct Answer: Option D

Explanation:
Beat frequency is the absolute difference between two frequencies. Given 4 beats with 256 Hz, the unknown fork is either 256+4=260 Hz or 256-4=252 Hz. Adding wax increases mass, which strictly lowers the frequency of a fork. If it was 252 Hz, lowering it would increase the gap from 256, increasing beats. If it was 260 Hz, lowering it brings it closer to 256, decreasing beats to 2. Thus, it was originally 260 Hz.
This question belongs to: Science Physics
Question #153
In standard AC household supply in India, the frequency of the alternating current is 50 Hz. How many times per second does the current change its direction?
A. 25 times
B. 50 times
C. 100 times
D. 0 times
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Correct Answer: Option C

Explanation:
A frequency of 50 Hz means there are 50 complete wave cycles per second. A single complete sinusoidal cycle consists of one positive half-cycle and one negative half-cycle. Therefore, the current reaches zero and reverses its direction exactly twice during each complete cycle. For 50 cycles, the current changes direction 50 * 2 = 100 times per second.
This question belongs to: Science Physics
Question #154
Which of the following physical quantities is an example of a vector quantity?
A. Electric charge
B. Electric potential
C. Electric field intensity
D. Electric current
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Correct Answer: Option C

Explanation:
A vector quantity possesses both magnitude and a specific spatial direction, and it must obey the laws of vector addition. Electric field intensity is a vector (force per unit charge, having the direction of the force). Electric current has a direction in circuits but adds algebraically like a scalar (violating vector addition). Charge and potential are standard scalars.
This question belongs to: Science Physics
Question #155
The working principle of a Venturimeter, used to measure the flow rate of a liquid through a pipe, is primarily based on:
A. Stokes' Law
B. Bernoulli's Principle
C. Torricelli's Theorem
D. Archimedes' Principle
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Correct Answer: Option B

Explanation:
A Venturimeter consists of a converging pipe, a narrow throat, and a diverging pipe. As fluid passes through the constricted throat, its velocity increases. According to Bernoulli's principle, this increase in kinetic energy must be accompanied by a strictly corresponding decrease in fluid pressure. By measuring this pressure difference, the flow rate can be precisely calculated.
This question belongs to: Science Physics
Question #156
A ray of light traveling from water (denser) into air (rarer) grazes the interface separating the two media. The angle of incidence in the water is called the:
A. Angle of refraction
B. Critical angle
C. Angle of polarization
D. Brewster's angle
Discuss
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Correct Answer: Option B

Explanation:
When light travels from an optically denser medium to a rarer medium, it bends away from the normal. As the angle of incidence increases, the angle of refraction also increases. The specific angle of incidence for which the refracted ray grazes the surface (meaning the angle of refraction is exactly 90 degrees) is defined as the critical angle.
This question belongs to: Science Physics
Question #157
Who among the following scientists first experimentally demonstrated the existence of electromagnetic waves, confirming Maxwell's theoretical predictions?
A. Guglielmo Marconi
B. Thomas Edison
C. Heinrich Hertz
D. Nikola Tesla
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Correct Answer: Option C

Explanation:
While James Clerk Maxwell predicted electromagnetic waves mathematically, it was the German physicist Heinrich Hertz who successfully built the first spark-gap transmitter in 1887. He physically generated and detected radio waves in his laboratory, proving Maxwell's theories right. The SI unit of frequency, the Hertz (Hz), is named in his absolute honor.
This question belongs to: Science Physics
Question #158
Assertion (A): Gamma rays are fundamentally un-deflected by electric and magnetic fields. Reason (R): Gamma rays carry no electrical charge.
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is false but R is true.
D. A is true but R is false.
Discuss
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Correct Answer: Option A

Explanation:
Electric fields deflect charged particles via Coulomb forces (F=qE), and magnetic fields deflect moving charged particles via Lorentz forces (F=qvB). Gamma rays are purely high-energy electromagnetic photons. Because they lack any electrical charge (q=0), both electric and magnetic forces on them are exactly zero. Therefore, they pass through fields completely un-deflected. R explains A perfectly.
This question belongs to: Science Physics
Question #159
Which basic thermodynamic law establishes the physical concept of temperature and is the foundational basis for constructing thermometers?
A. Second Law of Thermodynamics
B. Zeroth Law of Thermodynamics
C. First Law of Thermodynamics
D. Third Law of Thermodynamics
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Correct Answer: Option B

Explanation:
The Zeroth Law of Thermodynamics states that if body A is in thermal equilibrium with body B, and body B is in thermal equilibrium with body C, then A is also in thermal equilibrium with C. This transitive property implies a common physical property shared by them all, which we define as 'temperature'. A thermometer acts as body B.
This question belongs to: Science Physics
Question #160
For a heavily damped harmonic oscillator, what describes its return to the equilibrium position?
A. It oscillates rapidly with decreasing amplitude.
B. It returns to equilibrium slowly without any oscillation.
C. It oscillates exactly once before stopping.
D. It never returns to the equilibrium position.
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Correct Answer: Option B

Explanation:
Damping opposes the motion of an oscillator (like a pendulum in thick oil). In 'underdamped' systems, it oscillates with decaying amplitude. In 'critically damped' systems, it returns to equilibrium as fast as possible without oscillating. In 'overdamped' or heavily damped systems, the resistive force is so strong that it slowly creeps back to equilibrium without ever crossing it to oscillate.
This question belongs to: Science Physics

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