A wire of resistance 10 Ω is stretched to double its length. Its new resistance is
A. 40 Ω
B. 20 Ω
C. 10 Ω
D. 5 Ω
Answer: Option A
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:
In the visible spectrum (VIBGYOR), wavelength increases from Violet to Red. Since speed = frequency × wavelength (c = fλ), frequency is inversely proportional to wavelength. Red light has the longest wavelength and therefore the lowest frequency and lowest energy. Violet has the shortest wavelength and highest frequency.
Explanation:
Heat travels through spoon from hot end to cold end by conduction (molecular vibration and free electrons). Handle gets hot. Metal good conductor.
Explanation:
For a concave mirror, when an object is placed exactly at the center of curvature (C), the image is also formed at C. The image is real (can be captured on a screen), inverted (upside down), and exactly the same size as the object. Magnification in this specific case is exactly -1.
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