Physics MCQs

Question #381

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The instrument used to measure potential difference is

A. Ohmmeter

B. Galvanometer

C. Voltmeter

D. Ammeter

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Correct Answer: Option C

Explanation:
Voltmeter measures potential difference in volts. Connected in parallel. Ideal voltmeter has infinite resistance. Galvanometer can be converted to voltmeter by adding high resistance in series.

This question belongs to: Science Physics

Question #382

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Which of the following is the correct sequence of increasing wavelength?

A. Gamma rays < X-rays < Infrared < Radio

B. Radio < Infrared < X-rays < Gamma

C. Infrared < Radio < X-rays < Gamma

D. X-rays < Gamma < Radio < Infrared

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Correct Answer: Option A

Explanation:
EM spectrum: Gamma (0.1 m). Increasing wavelength: Gamma, X-ray, IR, Radio.

This question belongs to: Science Physics

Question #383

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A car travels first half distance at 40 km/h and second half at 60 km/h. Average speed is

A. 50 km/h

B. 45 km/h

C. 52 km/h

D. 48 km/h

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Correct Answer: Option D

Explanation:
Average speed = 2v₁v₂/(v₁+v₂) = 2×40×60/(40+60) = 4800/100 = 48 km/h. Not arithmetic mean (50). For equal distances, harmonic mean of speeds. If times equal, arithmetic mean applies.

This question belongs to: Science Physics

Question #384

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The process of heat transfer in a solid metal rod is

A. Convection

B. Conduction

C. Sublimation

D. Radiation

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Correct Answer: Option B

Explanation:
In solids, heat flows by conduction (lattice vibrations and free electrons). Metals are good conductors due to free electrons. Convection in fluids, radiation no medium.

This question belongs to: Science Physics

Question #385

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A 1000 W heater is used for 2 hours. Energy consumed in kWh is

A. 0.5 kWh

B. 2000 kWh

C. 2 kWh

D. 1000 kWh

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Correct Answer: Option C

Explanation:
Power = 1 kW (1000 W). Time = 2 h. Energy = Power × time = 1 × 2 = 2 kWh. 1 kWh = 3.6 × 10⁶ J, but here answer in kWh. Commercial unit.

This question belongs to: Science Physics

Question #386

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Which of the following is a vector?

A. Energy

B. Speed

C. Distance

D. Displacement

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Correct Answer: Option D

Explanation:
Displacement has both magnitude and direction, vector. Distance is scalar (path length). Speed scalar. Energy scalar. Vector examples: velocity, force, acceleration.

This question belongs to: Science Physics

Question #387

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An object weights 10 N in air, 8 N in water. The buoyant force is

A. 10 N

B. 8 N

C. 18 N

D. 2 N

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Correct Answer: Option D

Explanation:
Loss in weight = buoyant force = 10 - 8 = 2 N. Weight of displaced water = 2 N. Volume of object = mass of displaced water / density. Archimedes principle.

This question belongs to: Science Physics

Question #388

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The image formed on the retina of human eye is

A. Real and erect

B. Virtual and inverted

C. Real and inverted

D. Virtual and erect

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Correct Answer: Option C

Explanation:
Eye lens forms a real, inverted image on the retina. Brain processes it to perceive erect. Camera also forms real inverted image on film/sensor. The eye is like a convex lens system.

This question belongs to: Science Physics

Question #389

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A car accelerates from rest at 2 m/s² for 10 s, then moves with constant velocity for 10 s. Total distance covered is

A. 300 m

B. 200 m

C. 100 m

D. 400 m

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Correct Answer: Option A

Explanation:
Acceleration phase: s₁ = ½a t² = ½×2×100 = 100 m, v = a t = 20 m/s. Constant velocity phase: s₂ = v×t = 20×10 = 200 m. Total = 300 m. Motion in two parts.

This question belongs to: Science Physics

Question #390

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The number of electrons in one coulomb charge is approximately

A. 6.25 × 10⁻¹⁹

B. 6.25 × 10¹⁸

C. 9.1 × 10⁻³¹

D. 1.6 × 10⁻¹⁹

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Correct Answer: Option B

Explanation:
Charge of electron e = 1.6 × 10⁻¹⁹ C. Number n = 1/e = 1/(1.6×10⁻¹⁹) = 6.25 × 10¹⁸. This is a huge number. Important for current (1 A = 1 C/s).

This question belongs to: Science Physics

Question #391

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The loudness of sound depends on

A. Amplitude

B. Wavelength

C. Speed

D. Frequency

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Correct Answer: Option A

Explanation:
Loudness correlates with intensity, which is proportional to square of amplitude. Frequency determines pitch. Larger amplitude → louder sound. Measured in decibels.

This question belongs to: Science Physics

Question #392

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Which of the following has the shortest wavelength?

A. X-rays

B. Ultraviolet

C. Gamma rays

D. Infrared

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Correct Answer: Option C

Explanation:
Gamma rays have wavelengths < 10⁻¹² m, shortest in EM spectrum. X-rays 10⁻¹⁰-10⁻⁸ m. UV 10⁻⁸-4×10⁻⁷ m. IR longer. So gamma rays shortest. Highest frequency, energy.

This question belongs to: Science Physics

Question #393

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The resistance of an ideal voltmeter is

A. Low

B. Infinite

C. Same as ammeter

D. Zero

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Correct Answer: Option B

Explanation:
Voltmeter connected parallel, should draw minimum current, so ideally infinite resistance. Ammeter connected series, ideally zero resistance. Galvanometer moderate. Practical voltmeter has high but finite resistance.

This question belongs to: Science Physics

Question #394

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The phenomenon of mirage is due to

A. Total internal reflection

B. Reflection

C. Dispersion

D. Refraction and total internal reflection

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Correct Answer: Option D

Explanation:
Mirage occurs due to refraction of light through air layers of different temperatures (densities) and total internal reflection when ray tries to go from denser to rarer medium at grazing incidence. It's an optical illusion, not real water.

This question belongs to: Science Physics

Question #395

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A nucleus of mass number A and atomic number Z contains

A. A protons and Z neutrons

B. Z protons and A neutrons

C. A-Z protons and Z neutrons

D. Z protons and A-Z neutrons

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Correct Answer: Option D

Explanation:
Atomic number Z = number of protons. Mass number A = protons + neutrons. So neutrons = A - Z. Electrons = Z in neutral atom. Isotopes same Z, different N.

This question belongs to: Science Physics

Question #396

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The force between two charges in vacuum is F. If a medium of dielectric constant 5 is introduced, force becomes

A. F/5

B. 25F

C. F/25

D. 5F

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Correct Answer: Option A

Explanation:
Coulomb's law in medium: F' = F/K, where K = dielectric constant. So F' = F/5. Permittivity of medium ε = Kε₀. Force decreases in medium.

This question belongs to: Science Physics

Question #397

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Which of the following is used as a moderator in nuclear reactor?

A. Boron

B. Cadmium

C. Graphite

D. Uranium

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Correct Answer: Option C

Explanation:
Graphite, heavy water (D₂O), beryllium are moderators. Cadmium and boron are control rods (absorb neutrons). Uranium is fuel. Moderator slows neutrons.

This question belongs to: Science Physics

Question #398

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A ball is projected horizontally from top of a cliff. The time to hit ground depends on

A. Both velocity and height

B. Mass of ball

C. Height of cliff and g

D. Horizontal velocity

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Correct Answer: Option C

Explanation:
Vertical motion is independent of horizontal. t = √(2h/g). Mass doesn't affect. Horizontal velocity affects range, not time of fall. Projectile motion independence of perpendicular components.

This question belongs to: Science Physics

Question #399

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The energy stored in an inductor of inductance L carrying current I is

A. ½LI

B. ½LI²

C. L²I

D. LI²

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Correct Answer: Option B

Explanation:
Magnetic energy stored = ½ L I², analogous to capacitor energy ½ C V². L is inductance in henry (H). Energy stored in magnetic field.

This question belongs to: Science Physics

Question #400

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The eye defect 'astigmatism' is corrected using

A. Bifocal lens

B. Concave lens

C. Cylindrical lens

D. Convex lens

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Correct Answer: Option C

Explanation:
Astigmatism: cornea curvature not spherical, different focal lengths in different planes. Corrected by cylindrical lens which has different powers in perpendicular axes. Not simple spherical lens.

This question belongs to: Science Physics

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