Q. No.Three stars \(A,\) \(B,\) and \(C\) have surface temperatures \(T_A,~T_B\)and \(T_C\) respectively. Star \(A\) appears bluish, star \(B\) appears reddish and star \(C\) yellowish. Hence,
1. \(T_A>T_B>T_C\)
2. \(T_B>T_C>T_A\)
3. \(T_C>T_B>T_A\)
4. \(T_A>T_C>T_B\)
A slab of stone with an area \(0.36~\text{m}^{2}\) and thickness of \(0.1~\text{m}\) is exposed on the lower surface to steam at \(100^{\circ}\mathrm{C}\). A block of ice at \(0^{\circ}\mathrm{C}\) rests on the upper surface of the slab. In one hour \(4.8~\text{kg}\) of ice is melted. The thermal conductivity of the slab will be: (Given latent heat of fusion of ice \(= 3.36\times10^{5}~\text{JKg}^{-1}\))
1. \(1.29~\text{J/m/s/}^{\circ}\text{C}\)
2. \(2.05~\text{J/m/s/}^{\circ}\text{C}\)
3. \(1.02~\text{J/m/s/}^{\circ}\text{C}\)
4. \(1.24~\text{J/m/s/}^{\circ}\text{C}\)
Gravitational force is required for:
1. stirring of liquid
2. convection
3. conduction
4. radiation
Which of the following circular rods, (given radius \(r\) and length \(l\)) each made of the same material and whose ends are maintained at the same temperature will conduct the most heat:
| 1. | \(r=2r_0;~l=2l_0\) |
| 2. | \(r=2r_0;~l=l_0\) |
| 3. | \(r=r_0;~l=2l_0\) |
| 4. | \(r=r_0;~l=l_0\) |
Radiation energy corresponding to the temperature T of the sun is E. If its temperature is doubled, then its radiation energy will be:
1. 32 E
2. 16 E
3. 8 E
4. 4 E
A sphere maintained at a temperature of 600 K, has a cooling rate R in an external environment of 200 K temperature. If its temperature falls to 400 K, then its cooling rate will be:
1.
2.
3.
4. None
If λm denotes the wavelength at which the radioactive emission from a black body at a temperature T K is maximum, then:
1. λm is independent of T
2. λm ∝ T
3. λm ∝ T–1
4. λm ∝ T– 4
Two conducting slabs of heat conductivity \(K_{1} ~ \text{and} ~K_{2}\) are joined as shown in fig. If the temperature at the ends of the slabs are \(\theta_{1}\ and\ \theta_{2} \ (\theta_{1} > \theta_{2} ), \)then the final temperature \( \left(\theta\right)_{m} \)of the junction will be:
| 1. | \(\frac{K_{1} \theta_{1} + K_{2} \theta_{2}}{K_{1} + K_{2}}\) | 2. | \(\frac{K_{1} \theta_{2} + K_{2} \theta_{1}}{K_{1} + K_{2}}\) |
| 3. | \(\frac{K_{1} \theta_{2} + K_{2} \theta_{1}}{K_{1} - K_{2}}\) | 4. | None |
Wien's displacement law expresses the relation between:
| 1. | Wavelength corresponding to maximum energy and temperature |
| 2. | Radiation energy and wavelength |
| 3. | Temperature and wavelength |
| 4. | Colour of light and temperature |
Which of the following is closest to an ideal black body?
| 1. | Black lamp |
| 2. | Cavity maintained at a constant temperature |
| 3. | Platinum black |
| 4. | A lump of charcoal heated to high temperature |
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