Light emitting diodes (LEDs) are preferred over incandescent bulbs primarily because: MCQ with Answer and Explanation

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 are highly energy-efficient and convert most energy into light.
D. They consume more power but last longer.
Answer: Option C
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.

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Practice More Physics Questions

Question #1
The process of coating iron with zinc to prevent rusting is called
A. Galvanisation
B. Alloying
C. Annealing
D. Electroplating

Correct Answer: Option A


Explanation:
Galvanisation: iron/steel coated with zinc to prevent corrosion. Zinc acts as sacrificial anode. Electroplating deposits metal layer using electricity. Alloying mixing metals. Annealing heat treatment.

This question belongs to: Science Physics
Question #2
The least count of a vernier calliper is 0.01 cm. A measurement should be recorded as
A. 2.5 cm
B. 2.50 cm
C. 2.500 cm
D. 2.5000 cm

Correct Answer: Option B


Explanation:
Least count determines precision: two decimal places. So 2.50 cm. Extra digits indicate false precision.

This question belongs to: Science Physics
Question #3
Three forces in equilibrium: if two are equal and at 120°, third force is:
A. Zero
B. Difference of two
C. Equal to each, at 120° to both
D. Sum of two

Correct Answer: Option C


Explanation:
Vector equilibrium: three equal forces at 120° form closed triangle. Third force equals magnitude of others, oriented 120° from each. Memory aid: 'Equilibrium: vector sum = 0; symmetric forces ⇒ symmetric angles'. Statics concept frequently tested in competitive exams.

This question belongs to: Science Physics