Physics MCQ Practice 19 — Science Foundation Course for Class 11 & 12

1. A body of mass 2 kg is moving with velocity 10 m/s. Its kinetic energy is:

(a) 50 J (b) 100 J (c) 200 J (d) 20 J

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Correct Answer: (b) 100 J

Explanation:
KE = ½mv² = ½×2×100 = 100 J

2. The gravitational potential at the centre of Earth is:

(a) Zero (b) -GM/R (c) - (3/2)GM/R (d) Infinite

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Correct Answer: (c) - (3/2)GM/R

Explanation:
For uniform sphere, potential at centre = - (3/2)GM/R

3. The equivalent resistance of resistors 2 Ω, 4 Ω and 6 Ω in series is:

(a) 12 Ω (b) 1.09 Ω (c) 3 Ω (d) 24 Ω

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Correct Answer: (a) 12 Ω

Explanation:
Series: R = 2 + 4 + 6 = 12 Ω

4. The velocity of sound in air at 0°C is 332 m/s. At 27°C it is approximately:

(a) 332 m/s (b) 350 m/s (c) 364 m/s (d) 300 m/s

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Correct Answer: (b) 350 m/s

Explanation:
v ∝ √T → √(300/273) × 332 ≈ 350 m/s

5. The self-inductance of a coil is 0.5 H. The energy stored when current 4 A flows is:

(a) 4 J (b) 8 J (c) 2 J (d) 16 J

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Correct Answer: (a) 4 J

Explanation:
Energy = (1/2) L I² = ½ × 0.5 × 16 = 4 J

6. A convex lens forms a virtual image at 30 cm when object is at 15 cm. The focal length is:

(a) 30 cm (b) 10 cm (c) 15 cm (d) -30 cm

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Correct Answer: (a) 30 cm

Explanation:
1/f = 1/v - 1/u = 1/(-30) - 1/(-15) = 1/30 → f = 30 cm

7. In a series LCR circuit, the impedance at resonance is equal to:

(a) X_L (b) X_C (c) R (d) Zero

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Correct Answer: (c) R

Explanation:
At resonance, Z = R

8. The process of combining two light nuclei to form a heavy nucleus is called:

(a) Fission (b) Fusion (c) Alpha decay (d) Beta decay

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Correct Answer: (b) Fusion

Explanation:
Nuclear fusion

9. If the velocity of a body is halved, its kinetic energy becomes:

(a) Same (b) Half (c) One-fourth (d) Double

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Correct Answer: (c) One-fourth

Explanation:
KE ∝ v² → v/2 → KE becomes 1/4

10. The unit of magnetic flux density is:

(a) Tesla (b) Weber (c) Henry (d) Gauss

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Correct Answer: (a) Tesla

Explanation:
B is measured in Tesla (T)