A wire of resistance 5 Ω is bent into a circle. The effective resistance between ends of a diameter is
A. 1.25 Ω
B. 5 Ω
C. 2.5 Ω
D. 10 Ω
Answer: Option A
Solution (By JKExamLibrary)
Circle total resistance 5 Ω. Across diameter, two halves in parallel, each half 2.5 Ω. Parallel: R = (2.5×2.5)/(2.5+2.5) = 6.25/5 = 1.25 Ω. Equal parallel resistors gives half of each.
Explanation:
Coefficient of performance (COP) for refrigerator: COP = Q₂ / W, where Q₂ is heat extracted from cold reservoir, W is work input. By energy conservation, Q₁ = Q₂ + W (heat rejected to hot reservoir). COP > 1 typically. Option A is inverse; C and D relate to heat engine efficiency. Memory aid: 'Refrigerator COP = desired output (cooling) / work input'. This thermodynamics definition is frequently tested in competitive exams. Always distinguish refrigerator COP (cooling effect per work) from heat engine efficiency (work output per heat input).
Explanation:
Gamma rays are photons, electromagnetic waves with wavelengths shorter than X-rays, produced in nuclear transitions. No mass, no charge. Highly penetrating. Stopped by thick lead.
No comments yet. Be the first to start the discussion!