Hot coffee in a mug cools from \(90^{\circ}\mathrm{C}\) to \(70^{\circ}\mathrm{C}\) in 4.8 minutes. The room temperature is \(20^{\circ}\mathrm{C}\). Applying Newton's law of cooling, the time needed to cool it further by \(10^{\circ}\mathrm{C}\) should be nearly:
1. | 4.2 minute | 2. | 3.8 minute |
3. | 3.2 minute | 4. | 2.4 minute |
One kilogram of ice at \(0^\circ \mathrm{C}\) is mixed with one kilogram of water at \(80^\circ \mathrm{C}.\) The final temperature of the mixture will be: (Take: Specific heat of water = \(4200\) J kg-1 K-1, latent heat of ice\(=336\) kJ kg-1)
1. \(0^\circ \mathrm{C}\)
2. \(50^\circ \mathrm{C}\)
3. \(40^\circ \mathrm{C}\)
4. \(60^\circ \mathrm{C}\)
Two identical bodies are made of a material whose heat capacity increases with temperature. One of these is at \(100^{\circ} \mathrm{C}\), while the other one is at \(0^{\circ} \mathrm{C}\). If the two bodies are brought into contact, then assuming no heat loss, the final common temperature will be:
1. | \(50^{\circ} \mathrm{C}\) |
2. | more than \(50^{\circ} \mathrm{C}\) |
3. | less than \(50^{\circ} \mathrm{C}\) but greater than \(0^{\circ} \mathrm{C}\) |
4. | \(0^{\circ} \mathrm{C}\) |
The value of the coefficient of volume expansion of glycerin is \(5\times10^{-4}\) K-1. The fractional change in the density of glycerin for a temperature increase of \(40^\circ \mathrm{C}\) will be:
1. | \(0.015\) | 2. | \(0.020\) |
3. | \(0.025\) | 4. | \(0.010\) |
Steam at \(100^{\circ}\mathrm{C}\) is injected into 20 g of \(10^{\circ}\mathrm{C}\) water. When water acquires a temperature of \(80^{\circ}\mathrm{C}\), the mass of water present will be: (Take specific heat of water =1 cal g-1 \(^\circ\)C-1 and latent heat of steam = 540 cal g-1)
1. 24 g
2. 31.5g
3. 42.5 g
4. 22.5 g
The temperature of a body falls from \(50^{\circ}\mathrm{C}\) to \(40^{\circ}\mathrm{C}\) in 10 minutes. If the temperature of the surroundings is \(20^{\circ}\mathrm{C}\)hen the temperature of the body after another 10 minutes will be:
1. \(36.6^{\circ}\mathrm{C}\)
2. \(33.3^{\circ}\mathrm{C}\)
3. \(35^{\circ}\mathrm{C}\)
4. \(30^{\circ}\mathrm{C}\)
Two rods (one semi-circular and the other straight) of the same material and of the same cross-sectional area are joined as shown in the figure. Points A and B are maintained at different temperatures. The ratio of the heat transferred through a cross-section of a semi-circular rod to the heat transferred through a
cross-section of a straight rod at any given point in time will be:
1. 2:
2. 1: 2
3. : 2
4. 3: 2
A wall is made up of two layers, A and B. The thickness of the two layers is the same, but the materials are different. The thermal conductivity of A is double that of B. If in thermal equilibrium, the temperature difference between the two ends is \(36^{\circ}\mathrm{C}\)hen the difference in temperature between the two surfaces of A will be:
1. \(6^{\circ}\mathrm{C}\)
2. \(12^{\circ}\mathrm{C}\)
3. \(18^{\circ}\mathrm{C}\)
4. \(24^{\circ}\mathrm{C}\)
The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively are and ( > ). The rate of heat transfer through the slab, in a steady state is , with f which equals to:
1. 1
2.
3.
4.
The plots of intensity versus wavelength for three black bodies at temperatures , and respectively are as shown. Their temperatures are such that:
1. | \(\mathrm{T}_1>\mathrm{T}_2>\mathrm{T}_3 \) | 2. | \(\mathrm{T}_1>\mathrm{T}_3>\mathrm{T}_2 \) |
3. | \(\mathrm{T}_2>\mathrm{T}_3>\mathrm{T}_1 \) | 4. | \(\mathrm{T}_3>\mathrm{T}_2>\mathrm{T}_1\) |