Mud houses are cooler in the summer and warmer in the winter because:
1. | the mud is a superconductor of heat. |
2. | the mud is a good conductor of heat. |
3. | the mud is a bad conductor of heat. |
4. | None of the above |
The temperature of the hot and cold ends of a 20 cm long rod in a thermal steady state is at \(100^{\circ}\mathrm{C}\) and \(20^{\circ}\mathrm{C}\) respectively. The temperature at the centre of the rod will be:
1. \(50^{\circ}\mathrm{C}\)
2. \(60^{\circ}\mathrm{C}\)
3. \(40^{\circ}\mathrm{C}\)
4. \(30^{\circ}\mathrm{C}\)
One likes to sit in the sunshine in the winter season, because:
1. | The air around the body is hot, and the body absorbs heat from it. |
2. | we get energy from the sun. |
3. | we get heat by conduction from the sun. |
4. | None of the above |
Air is a bad conductor of heat or partly conducts heat. Still, a vacuum is to be placed between the walls of the thermos flask because:
1. | it is difficult to fill the air between the walls of the thermos flask. |
2. | due to more pressure of air, the thermos can get cracks. |
3. | by convection, heat can flow through the air. |
4. | on filling the air, there is no advantage. |
While measuring the thermal conductivity of a liquid, we keep the upper part hot and the lower part cool, so that:
1. | convection may be stopped. |
2. | radiation may be stopped. |
3. | heat conduction is easier downwards. |
4. | it is easier and more convenient to do so. |
On a clear sunny day, an object at temperature T is placed on the top of a high mountain. An identical object at the same temperature is placed at the foot of the mountain. If both the objects are exposed to sun-rays for two hours in an identical manner, the object placed on the top of a mountain will register a temperature:
1. | higher than the object at the foot. |
2. | lower than the object at the foot. |
3. | equal to the object at the foot. |
4. | none of the above. |
Taking into account the radiation that a human body emits which of the following statements is true?
1. | The radiation is emitted only during the day. |
2. | The radiation is emitted during the summers and absorbed during the winters. |
3. | The radiation emitted lies in the ultraviolet region and hence is not visible. |
4. | The radiation emitted is in the infra-red region. |
According to Wein's law:
1. = constant
2. = constant
3. = constant
4. = constant
A black body at \(200\) K is found to emit maximum energy at a wavelength of \(14\) \(\mu \)m. When its temperature is raised to \(1000\) K, the wavelength at which maximum energy is emitted will be:
1. | \(14\) \(\mu \)m | 2. | \(70\) \(\mu \)m |
3. | \(2.8\) \(\mu \)m | 4. | \(2.8\) nm |
If the temperature of the sun becomes twice its present temperature, then:
1. | Radiated energy would be predominantly in the infrared range. |
2. | Radiated energy would be primarily in the ultraviolet range. |
3. | Radiated energy would be predominantly in the X-ray region |
4. | Radiated energy would become twice as strong as it is now. |