Assertion (A): The coefficient of volume expansion of a solid is approximately three times its coefficient of linear expansion. Reason (R): Volume is a three-dimensional property derived from cubing the linear dimension. MCQ with Answer and Explanation

Assertion (A): The coefficient of volume expansion of a solid is approximately three times its coefficient of linear expansion. Reason (R): Volume is a three-dimensional property derived from cubing the linear dimension.
A. A is true but R is false.
B. A is false but R is true.
C. Both A and R are true but R is NOT the correct explanation of A.
D. Both A and R are true and R is the correct explanation of A.
Answer: Option D
Solution (By JKSSB Mock Tests)
The coefficient of linear expansion is alpha. A cube of side L has volume V = L^3. When heated, the new length is L(1+alphadT). The new volume is [L(1+alphadT)]^3. Expanding via binomial theorem and ignoring higher-order small terms gives V' = V(1 + 3alphadT). Thus, the volume expansion coefficient gamma is equal to 3alpha. Reason R correctly explains Assertion A.

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Practice More Physics Questions

Question #1
A particle covers half of its total distance with speed v1 and the rest half distance with speed v2. Its average speed during the complete journey is:
A. (v1^2 + v2^2) / (v1 + v2)
B. (v1 * v2) / (v1 + v2)
C. 2(v1 * v2) / (v1 + v2)
D. (v1 + v2) / 2

Correct Answer: Option C


Explanation:
When equal distances are covered with different speeds v1 and v2, the average speed is not the arithmetic mean, but the harmonic mean of the two speeds. Total distance = 2x. Total time = (x/v1) + (x/v2). Average speed = Total Distance / Total Time = 2x / [x(1/v1 + 1/v2)] = 2v1v2 / (v1 + v2).

This question belongs to: Science Physics
Question #2
The part of human eye that controls amount of light entering is
A. Lens
B. Iris
C. Cornea
D. Retina

Correct Answer: Option B


Explanation:
Iris adjusts pupil size. In bright light pupil constricts, dim light dilates. Retina forms image. Cornea and lens focus. Eye is like camera.

This question belongs to: Science Physics
Question #3
The instrument that converts mechanical energy into electrical energy is:
A. Galvanometer
B. Electric motor
C. Transformer
D. Generator

Correct Answer: Option D


Explanation:
Generator converts mechanical energy (rotation) to electrical energy via electromagnetic induction. Motor does the reverse (electrical to mechanical). Transformer changes AC voltage levels; galvanometer detects small currents. Memory aid: 'Generator: motion ⇒ electricity; Motor: electricity ⇒ motion'. This principle-based question tests understanding of energy conversion devices, crucial for electromagnetism in competitive exams. Always link device function to underlying physics law: generator (Faraday's law), motor (Lorentz force).

This question belongs to: Science Physics