In the heat formula Q = mcθ, each variable has a specific physical meaning. Option A (Speed of light) is incorrect — the speed of light is denoted by 'c' in Einstein's equation E = mc², where c = 3 × 10⁸ m/s. However, in the heat formula Q = mcθ, 'c' does NOT represent speed of light. The two formulas use the same letter 'c' but for completely different quantities — a common source of confusion for students. Option B (Charge of electron) is incorrect — the charge of an electron is denoted by 'e' (= 1.6 × 10⁻¹⁹ coulombs), not 'c'. Confusing 'c' with 'e' is a basic error in physics. Option C (Specific heat of the substance) is CORRECT — in Q = mcθ, 'c' stands for the specific heat capacity of the substance. It is defined as the amount of heat required to raise the temperature of 1 gram (or 1 kg) of a substance by 1°C (or 1 K). The SI unit of specific heat is J·kg⁻¹·K⁻¹ (joule per kilogram per kelvin). The specific heat of water is 1 cal/g/°C = 4186 J/kg/K. Option D (Coefficient of expansion) is incorrect — coefficients of thermal expansion are denoted by α (linear), β (area), and γ (volume). They represent dimensional change per unit temperature change and are not the same as specific heat.
FAQ
Common questions and clear answers for this topic.
Heat is a form of energy that transfers between objects or systems due to a temperature difference, moving from a hotter body to a cooler one until thermal equilibrium is reached.
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