JEE Main · 2025 · 02 Apr 2025 · Shift 2 · Heat & Thermodynamics

Heat capacity is the heat required to raise the temperature of the whole body by one kelvin, $C=\Delta Q/\Delta T$, so its unit is $\mathrm{J}{\mathrm{K}}^{-1}$. Specific heat capacity is the heat per unit mass per kelvin, $s=\Delta Q/(m\Delta T)$, with unit $\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$. Latent heat is the heat per unit mass needed for a change of phase, $L=\Delta Q/m$, with unit $\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}$. Thermal conductivity comes from $\Delta Q=\frac{kA\Delta Tt}{d}$, so $k=\frac{\Delta Qd}{A\Delta Tt}$ carries the unit $\mathrm{J}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}{\mathrm{s}}^{-1}$. Thus heat capacity goes with $\mathrm{J}{\mathrm{K}}^{-1}$, specific heat capacity with $\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$, latent heat with $\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}$, and thermal conductivity with $\mathrm{J}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}{\mathrm{s}}^{-1}$.