Thermal properties of matter practice · Medium

Option D ($W\,{m^{ - 1}}\,{K^{ - 1}}$) is correct because thermal conductivity is defined as the rate of heat transfer per unit area per unit temperature gradient, which leads to the given unit.

Cryogenics is the correct answer because it is the study of physical phenomena at very low temperatures, typically below the boiling point of liquid nitrogen.

Option D (${\mathrm{U}_2}\, > \,{\mathrm{U}_1}$) is correct because the wavelength of maximum emission shifts according to Wien's displacement law, and 500nm is closer to that wavelength than 250nm.

Option A (Expands while freezing) is correct because increasing pressure favors the phase with smaller volume. If a liquid expands upon freezing, increasing pressure will hinder the freezing process, thus decreasing the freezing point.

Option A (Conduction) is correct because convection requires gravity for fluid movement, and radiation is less efficient in liquids.

Option C (Are bad conductors of heat) is correct because wool has low thermal conductivity, trapping air and reducing heat loss from the body.

Option A ($2\;cal/K$) is correct because the value of R in calories is approximately 2 cal/K.

Option A ($1$) is correct because a perfectly black body absorbs all incident radiation, meaning its absorptive power is 1.

Option A (${43^0}C$) is correct because it is the approximate temperature of the body after the next 10 minutes, calculated using Newton's law of cooling.

Efficiency of carnot engine cannot be made larger than 50 % is the correct answer because if the efficiency is 40% with a source at 500K, then the sink temperature is 300K. With this sink temperature, an efficiency of 60% would require a source temperature of 750K. However, the problem states that 200 cal of heat is given, whose efficiency is 40 %, takes is heat from a source maintained at a temperature of 500 K. It is desired to have an engine of efficiency 60 % Then, the intake temperature for the same exhaust (sink). Temperature must be

Option B (Colour of the liquid) is correct because the apparent expansion of a liquid depends on the nature of the liquid, the change in temperature, and the material of the vessel, but not the color of the liquid.

Option D ($l/KA$) is correct because thermal resistance is defined as the ratio of length to the product of thermal conductivity and area.

Option D (Water expands when cooled from $4^0 {C}$ to $0^{\circ} {C}$) is correct because water has a unique property of expanding when cooled from 4°C to 0°C, making the colder water less dense and rise to the top.

Option D is correct. Absolute zero, which is 0 Kelvin, corresponds to -273.15°C on the Celsius scale.

Option B (White) is correct because as a black body is heated to high temperatures, it emits radiation across the visible spectrum, resulting in a white appearance.

Option C (Radiation) is correct because radiation does not require a medium for heat transfer and can occur at the speed of light, making it the fastest mode of heat transfer.

Option A (The hollow sphere will cool at a faster rate for all values of T) is correct because the hollow sphere has a lower thermal capacity for the same surface area.

Option D (Vapour pressure Thermometers) is correct because vapour pressure thermometers are specifically designed to measure very low temperatures by utilizing the relationship between vapour pressure and temperature of certain substances.

Option B (${60^0}C$) is correct because the temperature distribution is linear in steady state, and the center is halfway between the hot and cold ends.

Option C (${60^0}C$) is correct because the temperature is calculated using the formula relating the faulty thermometer reading to the Celsius scale, accounting for the shifted fixed points.

Option C (1) is correct because an open window absorbs all incident sound waves, thus having an absorption coefficient of 1.

Option C (The temperatures of B is maximum, A is minimum and C is intermediate) is correct because according to Wien's displacement law, the wavelength of maximum intensity is inversely proportional to temperature; blue has the shortest wavelength and red has the longest.

The hollow sphere will cool at a faster rate because it has a larger surface area for radiation compared to its mass, leading to quicker heat loss.

Option B (${68^0}C$) is correct because it is calculated using the principle of calorimetry, equating heat lost by the hot water to heat gained by the cold water and beaker.

Option B ($- {146^0}F$) is correct because it is the closest Fahrenheit equivalent to 95 K after converting from Kelvin to Celsius and then to Fahrenheit.

Option C (Both when heated or cooled) is correct because water has a unique property where it expands when cooled below 4°C and expands normally when heated above 4°C.

Option A ($9{m_A} = 4{m_B}$) is correct because it is derived from the ideal gas law and the given relationship between the pressure changes in the two vessels.

Option B (${60^0}C$) is correct because the temperature is calculated using the linear relationship between resistance and temperature.

Option A (Increase) is correct because the metal expands outwards, increasing the volume of the cavity.

Option B ($2{Q_1}$) is correct because doubling the linear dimensions while keeping the temperature constant doubles the rate of heat flow.