Two rods of identical dimensions are joined end-to-end, and the ends of the composite rod are kept at \(0^\circ\mathrm{ C}\) and \(100^\circ\mathrm{ C}\) (as shown in the diagram). The temperature of the joint is found to be \(40^\circ\mathrm{ C}.\) Assuming no loss of heat through the sides of the rods, the ratio of the conductivities of the rods \(K_1/K_2\) is:
1. \(\frac32\)
2. \(\frac23\)
3. \(\frac11\)
4. \(\frac{\sqrt3}{\sqrt2}\)
The temperature at which the Celsius and Fahrenheit thermometers agree (to give the same numerical value) is:
1. \(-40^\circ\)
2. \(40^\circ\)
3. \(0^\circ\)
4. \(50^\circ\)
The ice-point reading on a thermometer scale is found to be \(20^\circ,\) while the steam point is found to be \(70^\circ.\) When this thermometer reads \(100^\circ ,\) the actual temperature is:
1. \(80^\circ~\mathrm{C}\)
2. \(130^\circ~\mathrm{C}\)
3. \(160^\circ~\mathrm{C}\)
4. \(200^\circ~\mathrm{C}\)
A rod \(\mathrm{A}\) has a coefficient of thermal expansion \((\alpha_A)\) which is twice of that of rod \(\mathrm{B}\) \((\alpha_B)\). The two rods have length \(l_A,~l_B\) where \(l_A=2l_B\). If the two rods were joined end-to-end, the average coefficient of thermal expansion is:
1. \(\alpha_A\)
2. \(\frac{2\alpha_A}{6}\)
3. \(\frac{4\alpha_A}{6}\)
4. \(\frac{5\alpha_A}{6}\)
1. | \(\theta_{1}=0, ~\theta_{2}=90\) |
2. | \(\theta_{1}=10,~\theta_{2}=85\) |
3. | \(\theta_{1}=20, ~\theta_{2}=80\) |
4. | \(\theta_{1}=30, ~\theta_{2}=100\) |
A solid at temperature T1, is kept in an evacuated chamber at temperature T2 > T1 . The rate of increase of temperature of the body is proportional to
1. T2 – T1
2. \(T^2_2 -T^2_1\)n
3. \(T^3_2 -T^3_1\)
4. \(T^4_2 -T^4_1\)
In a room containing air, heat can go from one place to another:
1. by conduction only
2. by convection only
3. by radiation only
4. by all three modes