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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Page 18 of 65
Question #341
A radioactive substance has half-life of 10 days. Fraction remaining after 30 days is
A. 1/2
B. 1/4
C. 1/8
D. 1/16
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Correct Answer: Option C

Explanation:
Number of half-lives = 30/10 = 3. Remaining = (1/2)³ = 1/8. Exponential decay N = N₀(1/2)^(t/T). Radioactive decay constant λ = ln2/T.
This question belongs to: Science Physics
Question #342
In a simple pendulum, the restoring force is provided by
A. Tension in string
B. Component of weight tangential to path
C. Air resistance
D. Centripetal force
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Correct Answer: Option B

Explanation:
For small angular displacement, restoring force = -mg sinθ ≈ -mgθ, directed towards equilibrium. Tangential component of weight. Tension balances radial component. This causes SHM.
This question belongs to: Science Physics
Question #343
The number of base SI units is
A. 8
B. 5
C. 6
D. 7
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Correct Answer: Option D

Explanation:
Seven base units: metre, kilogram, second, ampere, kelvin, mole, candela. All other units derived. This is standard definition. Supplementary units radian and steradian now considered dimensionless derived units.
This question belongs to: Science Physics
Question #344
The dimensional formula of surface tension is
A. [MLT⁻²]
B. [MT⁻²]
C. [ML⁻¹T⁻²]
D. [ML⁰T⁻²]
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Correct Answer: Option B

Explanation:
Surface tension = force/length. Force dimensions [MLT⁻²], length [L], so [MLT⁻²]/[L] = [MT⁻²]. Also energy per area gives same dimensions: [ML²T⁻²]/[L²] = [MT⁻²].
This question belongs to: Science Physics
Question #345
A student measures the length of a pencil as 7.50 cm. The number of significant figures is
A. 1
B. 4
C. 2
D. 3
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Correct Answer: Option D

Explanation:
7.50 has three significant figures (7,5,0). Trailing zero after decimal is significant. If it were 7.5 cm, two significant figures. Precision indicated by decimal places.
This question belongs to: Science Physics
Question #346
A bullet of mass 20 g is fired with velocity 200 m/s. Its momentum is
A. 4 kg m/s
B. 4000 kg m/s
C. 40 kg m/s
D. 0.4 kg m/s
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Correct Answer: Option A

Explanation:
Mass m = 20 g = 0.02 kg. Momentum p = m v = 0.02 × 200 = 4 kg m/s. Always convert mass to kg. Momentum unit kg·m/s.
This question belongs to: Science Physics
Question #347
Work done by a man in carrying a suitcase weighing 10 kg on his head while walking 5 m horizontally (g=10) is
A. 250 J
B. 50 J
C. 0 J
D. 500 J
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Correct Answer: Option C

Explanation:
Force (weight) is vertical (upward to support), displacement horizontal, angle 90°, cos90°=0, work = 0. No work against gravity because vertical height doesn't change. Energy spent is internal muscular effort, but physics work zero.
This question belongs to: Science Physics
Question #348
An electric bulb rated 220 V, 100 W is operated at 110 V. The power consumed is
A. 100 W
B. 12.5 W
C. 50 W
D. 25 W
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Correct Answer: Option D

Explanation:
Resistance R = V²/P = 220²/100 = 484 Ω. At 110 V, P = V²/R = 110²/484 = 12100/484 = 25 W. Assuming resistance constant. Power reduces to quarter when voltage halved (P ∝ V² for fixed R).
This question belongs to: Science Physics
Question #349
Which of the following is a non-renewable source of energy?
A. Wind energy
B. Tidal energy
C. Coal
D. Solar energy
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Correct Answer: Option C

Explanation:
Coal is fossil fuel, finite, non-renewable. Solar, wind, tidal are renewable. This relates to everyday physics and energy concepts.
This question belongs to: Science Physics
Question #350
The device that uses the principle of electromagnetic induction is
A. Electric bulb
B. Resistor
C. Electric motor
D. Transformer
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Correct Answer: Option D

Explanation:
Transformer, generator, dynamo use electromagnetic induction (Faraday's law). Motor uses magnetic effect of current. Bulb uses heating effect. Resistor limits current. Induction: changing flux induces emf.
This question belongs to: Science Physics
Question #351
The SI unit of pressure is
A. Torr
B. Atmosphere
C. Bar
D. Pascal
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Correct Answer: Option D

Explanation:
Pascal (Pa) = N/m². Bar = 10⁵ Pa, Torr = mm Hg, atmosphere is another unit. SI unit is pascal. Named after Blaise Pascal.
This question belongs to: Science Physics
Question #352
A wire of resistance 5 Ω is bent into a circle. The effective resistance between ends of a diameter is
A. 5 Ω
B. 2.5 Ω
C. 10 Ω
D. 1.25 Ω
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Correct Answer: Option D

Explanation:
Circle total resistance 5 Ω. Across diameter, two halves in parallel, each half 2.5 Ω. Parallel: R = (2.5×2.5)/(2.5+2.5) = 6.25/5 = 1.25 Ω. Equal parallel resistors gives half of each.
This question belongs to: Science Physics
Question #353
The process of emission of electrons from hot metal surface is called
A. Field emission
B. Photoelectric emission
C. Thermionic emission
D. Secondary emission
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Correct Answer: Option C

Explanation:
Thermionic emission: electrons emitted when metal heated to high temperature (e.g., filament in cathode ray tube). Photoelectric: light incident. Field emission: strong electric field. Secondary: bombardment by particles.
This question belongs to: Science Physics
Question #354
Which of the following is not a vector quantity?
A. Momentum
B. Speed
C. Velocity
D. Force
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Correct Answer: Option B

Explanation:
Speed has magnitude only, scalar. Velocity is vector (speed + direction). Momentum and force are vectors. Distance is scalar, displacement vector.
This question belongs to: Science Physics
Question #355
A 2 kg object is raised to a height of 5 m. The work done against gravity (g=10) is
A. 10 J
B. 0 J
C. 100 J
D. 50 J
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Correct Answer: Option C

Explanation:
Work = mgh = 2 × 10 × 5 = 100 J. Force = mg = 20 N, distance 5 m, work = 20 × 5 = 100 J. This becomes potential energy stored.
This question belongs to: Science Physics
Question #356
The frequency of a source of sound is 500 Hz. The number of vibrations it makes in 2 minutes is
A. 30000
B. 60000
C. 1000
D. 500
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Correct Answer: Option B

Explanation:
Frequency = vibrations per second. 500 vibrations per second. In 2 min = 120 s, total vibrations = 500 × 120 = 60,000. Simple multiplication.
This question belongs to: Science Physics
Question #357
The device used to measure current in a circuit is
A. Galvanometer
B. Voltmeter
C. Ammeter
D. Potentiometer
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Correct Answer: Option C

Explanation:
Ammeter measures current. Galvanometer detects presence and direction of small currents, can be calibrated as ammeter/voltmeter. Voltmeter measures voltage. Potentiometer measures emf precisely.
This question belongs to: Science Physics
Question #358
The material of permanent magnet is
A. Soft iron
B. Copper
C. Steel
D. Aluminium
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Correct Answer: Option C

Explanation:
Steel has high retentivity, retains magnetism, used for permanent magnets. Soft iron has low retentivity, used for electromagnet core (temporary). Alnico, ferrites also used.
This question belongs to: Science Physics
Question #359
The force on a current-carrying conductor in a magnetic field is maximum when the conductor is
A. Perpendicular to field
B. At 60°
C. Parallel to field
D. At 45°
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Correct Answer: Option A

Explanation:
F = BIL sinθ. Maximum when θ = 90° (sin90°=1), so perpendicular. Parallel (θ=0°) force zero. This is the motor effect, used in electric motor.
This question belongs to: Science Physics
Question #360
Who gave the law of floatation?
A. Archimedes
B. Bernoulli
C. Pascal
D. Newton
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Correct Answer: Option A

Explanation:
Archimedes' principle: buoyant force = weight of displaced fluid. Law of floatation: floating body displaces fluid equal to its own weight. Archimedes discovered it. Pascal gave pressure law.
This question belongs to: Science Physics

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