The substance used as moderator in nuclear reactor must MCQ with Answer and Explanation

The substance used as moderator in nuclear reactor must
A. Increase neutron energy
B. Slow down neutrons without absorbing them
C. Absorb neutrons
D. Cool the reactor
Answer: Option B
Solution (By JKSSB Mock Tests)
Moderator slows neutrons via elastic collisions, low absorption. Heavy water, graphite.

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Practice More Physics Questions

Question #1
The wavelength of visible light lies between
A. 700 nm - 1 mm
B. 1 mm - 10 mm
C. 1 nm - 10 nm
D. 400 nm - 700 nm

Correct Answer: Option D


Explanation:
Visible spectrum approx 400 nm (violet) to 700 nm (red).

This question belongs to: Science Physics
Question #2
The ratio of SI to CGS unit of force is
A. 10³
B. 10⁷
C. 10²
D. 10⁵

Correct Answer: Option D


Explanation:
SI unit Newton (kg m/s²), CGS unit dyne (g cm/s²). 1 N = 10⁵ dyne. Conversion: 1 kg = 10³ g, 1 m = 100 cm, so 1 N = 10³ × 10² = 10⁵ dyne. Ratio N/dyne = 10⁵.

This question belongs to: Science Physics
Question #3
A screw gauge has a pitch of 1 mm and 100 divisions on its circular scale. The least count of this instrument is:
A. 0.1 mm
B. 0.001 mm
C. 0.0001 mm
D. 0.01 mm

Correct Answer: Option D


Explanation:
Least count of screw gauge = Pitch / Number of circular scale divisions. Given pitch = 1 mm, divisions = 100, so LC = 1 mm / 100 = 0.01 mm. This represents the smallest measurement the instrument can accurately detect. Screw gauges measure small dimensions like wire diameter with high precision. Memory tip: Least count formula is universal for vernier and screw instruments: value per division on main scale divided by total circular divisions. This concept is frequently tested in practical physics sections of competitive exams.

This question belongs to: Science Physics