The temperature of a liquid drops from 365 K to 361 K in 2 minutes. Find the time during which temperature of the liquid drops from 344 K to 342 K . Temperature of room is 293 K

1. 84 sec                       

2. 72 sec

3. 66 sec                       

4. 60 sec

Newton’s law of cooling, holds good only if the temperature difference between the body and the surroundings is

1. Less than 10$°\mathrm{C}$      

2. More than 10$°\mathrm{C}$

3. Less than 100$°\mathrm{C}$     

4. More than 100$°\mathrm{C}$

The temperature of a body falls from \(50^{\circ}\text{C}\)$\mathrm{}$ to \(40^{\circ}\text{C}\)$\mathrm{}$ in \(10\) minutes. If the temperature of the surroundings is \(20^{\circ}\text{C},\)$\mathrm{ t}$hen the temperature of the body after another \(10\) minutes will be:
1. \(36.6^{\circ}\text{C}\)          
2. \(33.3^{\circ}\text{C}\)$\mathrm{}$
3. \(35^{\circ}\text{C}\)             
4. \(30^{\circ}\text{C}\)$\mathrm{}$

A body takes 5 minutes to cool from 90$°\mathrm{C}$ to 60$°\mathrm{C}$. If the temperature of the surroundings is 20$°\mathrm{C}$, the time taken by it to cool from 60$°\mathrm{C}$ to 30$°\mathrm{C}$ will be. 

1. 5 min                   

2. 8 min

3. 11 min                 

4. 12 min

An object is cooled from 75°C to 65°C in 2 minutes in a room at 30°C. The time taken to cool another object from 55°C to 45°C in the same room in minutes is -

1. 4                   

2. 5

3. 6                   

4. 7

A cane is taken out from a refrigerator at 0°C. The atmospheric temperature is 25°C. If ${\mathrm{t}}_1$ is the time taken to heat from 0°C to 5°C and ${\mathrm{t}}_2$ is the time taken from 10°C to 15°C, then 

1. ${\mathrm{t}}_1>{\mathrm{t}}_2$                         

2. ${\mathrm{t}}_1<{\mathrm{t}}_2$

3. ${\mathrm{t}}_1={\mathrm{t}}_2$                        

4. There is no relation

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. The 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. \(2:\pi\)
2. \(1:2\)
3. \(\pi:2\)
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 \(36^{\circ}\mathrm{C}\)$\mathrm{,\; t}$hen the difference in temperature between the two surfaces of A will be:
1. \(6^{\circ}\mathrm{C}\)$\mathrm{}$

2. \(12^{\circ}\mathrm{C}\)$\mathrm{}$

3. \(18^{\circ}\mathrm{C}\)$\mathrm{}$

4. \(24^{\circ}\mathrm{C}\)$\mathrm{}$

Three rods of identical area of cross-section and made from the same metal form the sides of an isosceles triangle ABC , right angled at B. The points A and B are maintained at temperatures T and $\sqrt{2}\mathrm{T}$ respectively. In the steady state the temperature of the point C is ${\mathrm{T}}_{\mathrm{C}}$. Assuming that only heat conduction takes place, $\frac{{\mathrm{T}}_{\mathrm{C}}}{\mathrm{T}}$ is equal to -
1. $\frac{1}{\left(\sqrt{2}+1\right)}$                   

2. $\frac{3}{\left(\sqrt{2}+1\right)}$
3. $\frac{1}{2\left(\sqrt{2}-1\right)}$                  

4. $\frac{1}{\sqrt{3}\left(\sqrt{2}-1\right)}$

A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to a temperature of 1000°C. Which one of these will cool first ?

1. Plate                     

2. Sphere

3. Cube                     

4. None of these