LED working principle: MCQ with Answer and Explanation

Question
LED working principle:
A. Fluorescence
B. Incandescence
C. Phosphorescence
D. Electroluminescence
Answer: Option D
Solution (By JKExamLibrary)
LED: electroluminescence - electron-hole recombination in semiconductor emits photons. Incandescence: thermal radiation (bulbs); Fluorescence: UV excitation. Memory tip: 'LED = semiconductor light emission; no filament, efficient'. Modern device principle frequently tested in competitive exams linking physics to technology.
This question belongs to: Science Physics
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Practice More Physics Questions

Question #1
In parallel circuit, which quantity is same across branches?
A. Resistance
B. Current
C. Voltage
D. Power
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Correct Answer: Option C

Explanation:
Parallel branches share same voltage (potential difference). Current divides inversely with resistance. Memory aid: 'Parallel: same voltage; Series: same current'. Fundamental circuit property frequently tested in competitive exams to assess basic electronics understanding.
This question belongs to: Science Physics
Question #2
The SI unit of frequency is
A. Hertz
B. Metre
C. Watt
D. Second
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Correct Answer: Option A

Explanation:
Hertz (Hz) = cycle per second = s⁻¹. Named after Heinrich Hertz. For sound, radio waves. Kilohertz, megahertz, gigahertz.
This question belongs to: Science Physics
Question #3
The property of a body to resist change in its state of motion is called
A. Momentum
B. Inertia
C. Weight
D. Force
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Correct Answer: Option B

Explanation:
Inertia is directly proportional to mass. Heavier object harder to accelerate/decelerate. Newton's first law defines inertia. Momentum is mass × velocity, depends on motion.
This question belongs to: Science Physics
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