LED stands for MCQ with Answer and Explanation

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LED stands for

A. Low Energy Device

B. Light Emitting Diode

C. Linear Electron Device

D. Laser Emission Display

Answer: Option B

Solution (By JKSSB Mock Tests)

LED (Light Emitting Diode) emits light when forward biased, due to recombination of electrons and holes. Efficient, long life. Used in displays, lighting. Laser is Light Amplification by Stimulated Emission of Radiation.

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Question #1

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A hydraulic lift has area ratio of output to input piston 10:1. Force applied 50 N on input piston lifts weight of

A. 5 N

B. 500 N

C. 5000 N

D. 50 N

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Correct Answer: Option B

Explanation:
F1/A1 = F2/A2 => F2 = (A2/A1) F1 = 10×50 = 500 N.

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Question #2

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A radioactive nucleus emits a beta particle. Its atomic number

A. Increases by 1

B. Decreases by 2

C. Decreases by 1

D. Remains same

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Correct Answer: Option A

Explanation:
β⁻ decay: neutron → proton + electron, Z increases by 1.

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Question #3

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Solar cell converts:

A. Heat to electricity

B. Mechanical to electricity

C. Chemical to electricity

D. Light to electricity

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Correct Answer: Option D

Explanation:
Photovoltaic effect: photons excite electrons in semiconductor, creating voltage. Direct light-to-electricity conversion. Memory tip: 'Photo = light; voltaic = electricity'. Renewable energy principle frequently tested in competitive exams to assess energy conversion understanding.

This question belongs to: Science Physics

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