Which of the following is a renewable source of energy? MCQ with Answer and Explanation

Explanation:
Ideal gas: no intermolecular forces ⇒ internal energy = kinetic energy ∝ T. U = f/2 nRT. Memory tip: 'Ideal gas: U = U(T) only; real gases have V dependence'. Thermodynamics concept frequently tested in competitive exams.

Explanation:
Number of half-lives = 30/10 = 3. Remaining = (1/2)³ = 1/8. Exponential decay N = N₀(1/2)^(t/T). Radioactive decay constant λ = ln2/T.

Explanation:
Q = mcΔθ = 2 × 4200 × 10 = 84,000 J = 84 kJ. Large specific heat of water makes it useful for cooling and climate moderation. Always check units: mass kg, c J/kg°C, ΔT °C.