A wire of resistance 10 Ω is stretched to double its length. Its new resistance is
A. 10 Ω
B. 40 Ω
C. 5 Ω
D. 20 Ω
Answer: Option B
Solution (By JKSSB Mock Tests)
Resistance R = ρL/A. Volume constant: A ∝ 1/L. Stretching length to 2L reduces area to A/2. New R' = ρ(2L)/(A/2) = 4ρL/A = 4R = 40 Ω. Resistance proportional to (length)² when volume constant.
Explanation:
Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure. Airplane wings (airfoils) are shaped so that air travels faster over the curved top surface than the flat bottom. This creates lower pressure above the wing and higher pressure below, resulting in an upward lift force.
Explanation:
Newton's law: F = Gm₁m₂/r² ⇒ F ∝ 1/r². Inverse square law fundamental to gravitation, electrostatics, and radiation intensity. Memory aid: 'Gravity weakens with square of distance; double distance ⇒ force becomes 1/4'. Core concept frequently tested to verify understanding of fundamental force laws in competitive exams.
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