A 5 Ω resistor dissipates 20 W power. Current through it is MCQ with Answer and Explanation

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A 5 Ω resistor dissipates 20 W power. Current through it is

A. 0.5 A

B. 2 A

C. 100 A

D. 4 A

Answer: Option B

Solution (By JKSSB Mock Tests)

P = I² R => I = √(P/R) = √(20/5) = √4 = 2 A.

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Question #1

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If the force of attraction between two objects each of mass 1 kg separated by 1 m is F, then force between 2 kg and 2 kg at same distance is

A. F

B. 2F

C. 4F

D. 8F

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Correct Answer: Option C

Explanation:
F ∝ m₁m₂. Initial: 1×1 = 1. New masses 2 and 2, product 4, so force = 4F. Distance unchanged. Universal gravitation F = Gm₁m₂/r².

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Question #2

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Atmospheric pressure at sea level in pascal is approximately

A. 1.01 × 10⁵ Pa

B. 1.01 × 10³ Pa

C. 1.01 × 10⁷ Pa

D. 1.01 × 10⁹ Pa

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Correct Answer: Option A

Explanation:
Standard atmospheric pressure 1 atm = 1.01325 × 10⁵ Pa ≈ 1.01 × 10⁵ Pa = 101 kPa. Also equals 760 mm of Hg. This is an important conversion for pressure units.

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Question #3

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Free fall: height h takes time t. Height 4h takes time:

A. 2t

B. t/2

C. t

D. 4t

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Correct Answer: Option A

Explanation:
h = ½gt² ⇒ t ∝ √h. If h' = 4h, t' = √4 × t = 2t. Time doubles when height quadruples. Memory aid: 'Free fall: t ∝ √h; 4× height ⇒ 2× time'. Kinematics proportionality frequently tested in competitive exams.

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