If the length and cross-sectional area of a wire are both doubled, its resistance will: MCQ with Answer and Explanation

If the length and cross-sectional area of a wire are both doubled, its resistance will:
A. Remain unchanged
B. Halve
C. Double
D. Quadruple
Answer: Option A
Solution (By JKSSB Mock Tests)
Resistance (R) of a wire is given by R = ρL/A, where ρ is resistivity, L is length, and A is cross-sectional area. If L becomes 2L and A becomes 2A, the new resistance is R' = ρ(2L)/(2A). The 2s cancel out, leaving R' = ρL/A = R. Thus, the resistance remains entirely unchanged.

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Due to the Earth's rotation, the acceleration due to gravity (g) is minimum at:
A. The South Pole
B. A latitude of 45 degrees
C. The Equator
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Correct Answer: Option C


Explanation:
The effective acceleration due to gravity at latitude lambda is g' = g - R * w^2 * cos^2(lambda), where w is angular velocity. At the equator, lambda = 0, so cos(0) = 1. This subtracts the maximum outward centrifugal acceleration (Rw^2) from g. At the poles, lambda = 90, centrifugal effect is zero. Thus, g is minimum exactly at the equator.

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Question #2
The voltage of domestic AC supply in India is
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D. 110 V, 60 Hz

Correct Answer: Option B


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The gravitational force between two bodies does not depend on
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Correct Answer: Option C


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This question belongs to: Science Physics