Physics MCQs

Question #721

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The splitting of white light by a prism is due to

A. Dispersion

B. Reflection

C. Interference

D. Diffraction

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Correct Answer: Option A

Explanation:
Different colours have different speeds/refractive indices in glass, causing dispersion.

This question belongs to: Science Physics

Question #722

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A 6 V battery is connected to a 3 Ω resistor. Current is

A. 3 A

B. 18 A

C. 2 A

D. 0.5 A

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Correct Answer: Option C

Explanation:
I = V/R = 6/3 = 2 A.

This question belongs to: Science Physics

Question #723

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Three resistors 2 Ω, 3 Ω, 6 Ω are connected in parallel. Equivalent resistance is

A. 0.5 Ω

B. 1.5 Ω

C. 1 Ω

D. 11 Ω

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Correct Answer: Option C

Explanation:
1/R = 1/2+1/3+1/6 = 3/6+2/6+1/6 = 6/6=1 => R=1 Ω.

This question belongs to: Science Physics

Question #724

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The unit of resistance is

A. Ampere

B. Ohm

C. Volt

D. Watt

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Correct Answer: Option B

Explanation:
Ohm (Ω) = V/A.

This question belongs to: Science Physics

Question #725

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A wire of resistance 16 Ω is drawn to double its length. New resistance is

A. 4 Ω

B. 32 Ω

C. 64 Ω

D. 8 Ω

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Correct Answer: Option C

Explanation:
Volume constant: R' = n² R = 2² × 16 = 64 Ω.

This question belongs to: Science Physics

Question #726

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An electric bulb rated 100 W, 220 V has resistance

A. 242 Ω

B. 100 Ω

C. 220 Ω

D. 484 Ω

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Correct Answer: Option D

Explanation:
R = V²/P = 48400/100 = 484 Ω.

This question belongs to: Science Physics

Question #727

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A current of 2 A flows through a 10 Ω resistor for 1 minute. Heat produced is

A. 2400 J

B. 20 J

C. 1200 J

D. 400 J

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Correct Answer: Option A

Explanation:
H = I² R t = 4 × 10 × 60 = 2400 J.

This question belongs to: Science Physics

Question #728

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Two 60 W bulbs are connected in series across 220 V. Each bulb power becomes (approximately)

A. 15 W

B. 120 W

C. 30 W

D. 60 W

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Correct Answer: Option A

Explanation:
Each bulb R = 220²/60 ≈ 807 Ω. Series total R=1614 Ω, current = 220/1614 ≈0.136 A. Power per bulb = I²R = (0.136)²×807 ≈ 15 W.

This question belongs to: Science Physics

Question #729

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The force on a moving charge in a magnetic field is maximum when angle between velocity and field is

A. 45°

B. 180°

C. 90°

D. 0°

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Correct Answer: Option C

Explanation:
F = qvB sinθ, max at θ=90°.

This question belongs to: Science Physics

Question #730

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The direction of induced current is given by

A. Ohm's law

B. Fleming's right hand rule

C. Ampere's rule

D. Fleming's left hand rule

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Correct Answer: Option B

Explanation:
Right hand rule for generators (induced current). Left hand rule for motors (force).

This question belongs to: Science Physics

Question #731

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A transformer with 100 primary turns and 500 secondary turns is a

A. Step-up transformer

B. Auto transformer

C. Isolation transformer

D. Step-down transformer

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Correct Answer: Option A

Explanation:
Ns > Np => step-up. Vs > Vp.

This question belongs to: Science Physics

Question #732

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A proton and an electron enter a uniform magnetic field with same velocity perpendicular to field. Which has larger radius?

A. Depends on charge

B. Proton

C. Electron

D. Same

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Correct Answer: Option B

Explanation:
r = mv/(qB). Proton mass >> electron mass, so radius larger.

This question belongs to: Science Physics

Question #733

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Alpha particles consist of

A. Protons

B. Electrons

C. Helium nuclei

D. Neutrons

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Correct Answer: Option C

Explanation:
2 protons + 2 neutrons, charge +2e.

This question belongs to: Science Physics

Question #734

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Nuclear fusion requires

A. High temperature and high pressure

B. High temperature only

C. Low temperature and high pressure

D. Low temperature and low pressure

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Correct Answer: Option A

Explanation:
Overcome Coulomb repulsion between nuclei, need extreme temperature and pressure.

This question belongs to: Science Physics

Question #735

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A nuclear reactor uses control rods made of

A. Heavy water

B. Uranium

C. Graphite

D. Cadmium

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Correct Answer: Option D

Explanation:
Cadmium or boron absorb neutrons to control chain reaction.

This question belongs to: Science Physics

Question #736

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The half-life of a radioactive sample is 3 days. After 9 days, fraction remaining is

A. 1/16

B. 1/4

C. 1/2

D. 1/8

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Correct Answer: Option D

Explanation:
3 half-lives (9/3=3) => (1/2)³ = 1/8.

This question belongs to: Science Physics

Question #737

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The time period of a simple pendulum is 2 s at a place where g=9.8 m/s². Its length is about

A. 1 m

B. 0.25 m

C. 2 m

D. 0.5 m

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Correct Answer: Option A

Explanation:
T=2π√(L/g) => L = gT²/(4π²) ≈ (9.8×4)/(4×9.87) ≈ 1 m.

This question belongs to: Science Physics

Question #738

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A wave completes 20 oscillations in 4 seconds. Frequency is

A. 0.2 Hz

B. 4 Hz

C. 80 Hz

D. 5 Hz

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Correct Answer: Option D

Explanation:
f = 20/4 = 5 Hz.

This question belongs to: Science Physics

Question #739

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In SHM, the restoring force is proportional to

A. Square of displacement

B. Time

C. Velocity

D. Displacement

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Correct Answer: Option D

Explanation:
F ∝ -x, defining SHM.

This question belongs to: Science Physics

Question #740

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A lactometer is used to check

A. Humidity

B. Blood pressure

C. Purity of milk

D. Purity of water

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Correct Answer: Option C

Explanation:
Measures specific gravity of milk, indicates adulteration.

This question belongs to: Science Physics

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