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#	Question	Answer
1	What is the SI unit of heat?	Joule (J).
2	What is the relation between Kelvin and Celsius temperatures?	\( T = t_c + 273.15 \).
3	What is the coefficient of volume expansion?	\( \alpha_v = \frac{\Delta V}{V \Delta T} \).
4	What is thermal stress?	The stress developed in a body when its thermal expansion is prevented.
5	What is specific heat capacity?	\( s = \frac{1}{m} \frac{\Delta Q}{\Delta T} \).
6	What is the principle of calorimetry?	Heat lost by the hot body = heat gained by the cold body (in an isolated system).
7	What is sublimation?	The change of state from solid to vapour without passing through the liquid state.
8	What is the latent heat of fusion of water?	\( 3.33 \times 10^5 \) J kg⁻¹.
9	What is the expression for the rate of heat flow by conduction?	\( H = KA \frac{\Delta T}{L} \).
10	What is the temperature of the steel-copper junction in the steady state for the system given in Example 10.6?	44.4°C.
11	What is natural convection?	Convection in which the motion of the fluid is caused by density differences due to heating (buoyancy).
12	What is the net rate of heat loss by radiation for a body with emissivity \( e \)?	\( H = e \sigma A (T^4 - T_s^4) \).
13	Under what condition is Newton's law of cooling valid?	For small temperature differences between the body and the surroundings.
14	Two absolute scales A and B have triple points of water defined as 200 A and 350 B. What is the relation between \( T_A \) and \( T_B \)?	\( \frac{T_A}{200} = \frac{T_B}{350} \).
15	What is the maximum amount of ice that can be melted by a 2.5 kg copper block at 500°C? (\( s = 0.39 \) J g⁻¹ K⁻¹, \( L_f = 335 \) J g⁻¹)	1.45 kg.
16	How does the coefficient of volume expansion of gases compare to that of solids and liquids?	Gases expand much more — \(\alpha_v\) for an ideal gas at room temperature (~3300×10⁻⁶ K⁻¹) is orders of magnitude larger than for typical liquids and solids.
17	A 0.047 kg aluminium sphere at 100°C is dropped into a 0.14 kg copper calorimeter containing 0.25 kg water at 20°C; the mixture settles at 23°C (Example 10.3). What is aluminium's specific heat capacity?	≈0.911 kJ/kg/K (911 J kg⁻¹ K⁻¹).
18	An iron bar and a brass bar (equal length and area) are soldered end to end, with free ends held at 373 K and 273 K (Example 10.7). What is the junction temperature?	315 K, from \(T_0=(K_1T_1+K_2T_2)/(K_1+K_2)\).
19	Why are the bottoms of cooking utensils often blackened?	So they absorb the maximum heat from the flame by radiation, transferring it efficiently to the food.
20	Does every energy transfer between two systems count as 'heat'?	No — heat transfer always involves a temperature difference between the systems; an energy transfer without a temperature difference is not heat.
21	Assertion: Adding a foam insulation layer over a concrete roof makes a room hotter in summer. Reason: Foam's trapped air pockets give it low thermal conductivity. Are these true?	Assertion is false — the foam layer prohibits heat transfer into the room, keeping it cooler, not hotter. Reason is true — air pockets give foam low conductivity. (NEET 2024)
22	A black sphere of radius 12 cm radiates 450 W at 500 K. If the radius is halved and the temperature doubled, what is the new radiated power?	1800 W, since \(H=A\sigma T^4 \propto r^2T^4\), giving a factor of \((1/2)^2\times2^4=4\). (NEET 2017)
23	Heat flows through a metal rod at 4.0 J/s when its ends are at 100°C and 110°C. What is the heat flow when the ends are instead at 200°C and 210°C?	Still 4.0 J/s, since \(H=KA\Delta T/L\) depends only on the temperature difference (10°C in both cases), not the absolute temperature. (NEET 2015)