Light emitting diodes (LEDs) are preferred over incandescent bulbs primarily because:
A. They emit a wider spectrum of light.
B. They rely on a heated filament.
C. They consume more power but last longer.
D. They are highly energy-efficient and convert most energy into light.
Answer: Option D
Solution (By JKSSB Mock Tests)
Incandescent bulbs work by heating a tungsten filament until it glows, converting roughly 90% of electrical energy into wasted heat and only 10% into light. LEDs are solid-state semiconductors that emit light through electroluminescence. They convert almost all their electrical energy directly into light, making them significantly more efficient and cooler.
Explanation:
Kirchhoff's Current Law (First Law) states that the total current entering a junction must exactly equal the total current leaving that junction. Current is the rate of flow of charge. Therefore, this law simply affirms that electric charge cannot be created or destroyed at a circuit node; all charge arriving must depart. It is the conservation of charge.
Explanation:
Binding energy per nucleon peaks around iron-56 (≈8.8 MeV/nucleon), making it the most stable nucleus. Lighter nuclei release energy via fusion; heavier via fission. Hydrogen has near-zero binding energy per nucleon; uranium ≈7.6 MeV/nucleon. Memory aid: 'Iron peak: most stable nucleus; fusion before, fission after'. This nuclear physics concept is frequently tested in competitive exams. Always link binding energy curve to energy release in stars (fusion) and reactors (fission).
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