Physics MCQ Practice 20 — Science Foundation Course for Class 11 & 12

1. A body covers 100 m in 5 seconds with uniform acceleration from rest. The final velocity is:

(a) 20 m/s (b) 40 m/s (c) 10 m/s (d) 30 m/s

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Correct Answer: (b) 40 m/s

Explanation:
s = ½at² → a = 8 m/s² → v = 0 + 8×5 = 40 m/s

2. The ratio of g on Earth to Moon is 6:1. The ratio of their masses (assuming same radius) is:

(a) 6:1 (b) 1:6 (c) 36:1 (d) 1:36

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Correct Answer: (a) 6:1

Explanation:
g ∝ M/R ² → same R → M_E / M_M = 6

3. Three resistors 2 Ω, 3 Ω and 6 Ω in parallel. Equivalent resistance is:

(a) 1 Ω (b) 11 Ω (c) 2 Ω (d) 6 Ω

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Correct Answer: (a) 1 Ω

Explanation:
1/R = 1/2 + 1/3 + 1/6 = 1 → R = 1 Ω

4. The frequency of a wave is 200 Hz. The time period is:

(a) 0.005 s (b) 0.05 s (c) 5 s (d) 0.5 s

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Correct Answer: (a) 0.005 s

Explanation:
T = 1/f = 1/200 = 0.005 s

5. The magnetic field at the centre of a circular coil with 10 turns, radius 0.1 m, current 2 A is (μ₀ = 4π×10⁻⁷):

(a) 1.26 × 10⁻⁴ T (b) 2.51 × 10⁻⁴ T (c) 4π × 10⁻⁵ T (d) 0.5 × 10⁻⁴ T

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Correct Answer: (b) 2.51 × 10⁻⁴ T

Explanation:
B = (μ₀ N I)/(2r) ≈ 2.51 × 10⁻⁴ T

6. A concave mirror has radius of curvature 40 cm. Its focal length is:

(a) 20 cm (b) 40 cm (c) 80 cm (d) -20 cm

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Correct Answer: (a) 20 cm

Explanation:
f = R/2 = 20 cm

7. In a purely inductive circuit, the phase difference between voltage and current is:

(a) 0° (b) 90° (current lags) (c) 90° (current leads) (d) 180°

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Correct Answer: (b) 90° (current lags)

Explanation:
Current lags voltage by 90° in inductor

8. The particle emitted in alpha decay is:

(a) Electron (b) Helium nucleus (c) Neutron (d) Proton

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Correct Answer: (b) Helium nucleus

Explanation:
Alpha particle is ⁴He nucleus

9. If the radius of a soap bubble is doubled, the excess pressure becomes:

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

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Correct Answer: (c) One-fourth

Explanation:
Excess pressure = 4T/r → r doubled → pressure 1/4

10. The SI unit of inductance is:

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

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Correct Answer: (a) Henry

Explanation:
Unit of self-inductance L is Henry (H)