SSC CGL Science – Heat & Thermodynamics – Tier II Level · Marathon

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SSC CGL Science – Heat & Thermodynamics – Tier II Level · Marathon – 11 questions, subject: General Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  
A Carnot engine works between 527 °C and 127 °C. Its efficiency is:

Correct Answer: B [50%]

Explanation:

800 K and 400 K: 1 − 400/800 = 50%.

2.  
A steel bridge 100 m long warms by 30 °C. With α = 1.2 × 10⁻⁵ per °C, it expands by:

Correct Answer: D [3.6 cm]

Explanation:

ΔL = 100 × 1.2 × 10⁻⁵ × 30 = 0.036 m.

3.  
A gas occupies 2 L at a pressure of 3 atm. At constant temperature, its volume at 1.5 atm is:

Correct Answer: A [4 L]

Explanation:

Boyle: P₁V₁ = P₂V₂ → 2 × 3/1.5 = 4 L.

4.  
The volume of a gas at 0 °C is 273 cm³. At constant pressure, at 100 °C it becomes:

Correct Answer: C [373 cm³]

Explanation:

V ∝ T(K): 273 × 373/273 = 373 cm³.

5.  
If the absolute temperature of a black body is doubled, the energy it radiates per second becomes:

Correct Answer: B [16 times]

Explanation:

Answer: 16 times. Stefan–Boltzmann: E ∝ T⁴.

6.  
A star's surface is at about 6000 K. By Wien's law (b ≈ 2.9 × 10⁻³ m K), its radiation peaks near:

Correct Answer: D [480 nm]

Explanation:

λ = 2.9 × 10⁻³ / 6000 ≈ 4.8 × 10⁻⁷ m.

7.  
An ideal refrigerator keeps its inside at −3 °C in a room at 27 °C. Its coefficient of performance is:

Correct Answer: B [9]

Explanation:

β = T₂/(T₁ − T₂) = 270/30 = 9.

8.  
In an adiabatic process:

Correct Answer: D [no heat enters or leaves the system]

Explanation:

Adiabatic = no heat exchange; isothermal = constant temperature.

9.  
Heat needed to change 0.5 kg of ice at −10 °C into water at 20 °C is about (c(ice) = 2100, L = 3.36 × 10⁵ J/kg, c(water) = 4200 J/kg K):

Correct Answer: C [≈ 2.2 × 10⁵ J]

Explanation:

0.5(2100 × 10 + 3.36 × 10⁵ + 4200 × 20) = 0.5 × 4.41 × 10⁵ = 2.205 × 10⁵ J.

10.  
Assertion–ReasonAssertion (A): No heat engine can have 100% efficiency.
Reason (R): Some heat must always be rejected to the cold sink (second law).

Correct Answer: A [Both A and R are true and R explains A]

Explanation:

Kelvin–Planck statement of the second law.

11.  
Data tableA cup of tea cools in a room at 30 °C – time (min): 0, 2, 4, 6; temperature (°C): 80, 70, 62, 56. Between 4 and 6 min it cools more slowly than between 0 and 2 min because:

Correct Answer: A [it is closer to room temperature]

Explanation:

Newton's law of cooling: rate ∝ (T − T₀); the excess falls from 50 °C (at 0 min) to 26–32 °C (at 4–6 min), so cooling slows.

➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 General Science book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-general-science

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