Concepts Of Physics MCQ Edition [Volume 2]
- Exam
- Concepts Of Physics MCQ Edition [Volume 2]
- Subject
- Physics
- Chapter
- Heat Transfer
Concepts Of Physics MCQ Edition [Volume 2] · Physics · Heat Transfer
A piece of charcoal and a piece of shining steel having the same...
A piece of charcoal and a piece of shining steel having the same surface area are placed in an open lawn under the bright sun for a long duration.
Options
- AThe steel will absorb a greater amount of heat than the charcoal
- BThe steel will reach a higher temperature than the charcoal
- CIf the two pieces are removed from the lawn and placed in a cold chamber, the charcoal will lose heat more rapidly than the steel
- DIf both are held with bare hands, the steel will feel hotter than the charcoal
Correct answer
D. If both are held with bare hands, the steel will feel hotter than the charcoal
Step-by-step solution
Charcoal acts approximately as a black body, meaning it is a good absorber and a good emitter of thermal radiation. Shining steel is highly reflective, making it a poor absorber and a poor emitter.
When placed in the sun, charcoal absorbs a greater amount of heat than the shining steel and consequently reaches a higher temperature.
According to Kirchhoff's law of radiation, a good absorber is also a good emitter. Therefore, when placed in a cold chamber, the charcoal will radiate and lose heat more rapidly than the steel.
Although the charcoal is at a higher temperature, steel has a significantly higher thermal conductivity. When touched with bare hands, heat transfers from the steel to the skin at a much faster rate than from the charcoal, causing the steel to feel hotter.
When placed in the sun, charcoal absorbs a greater amount of heat than the shining steel and consequently reaches a higher temperature.
According to Kirchhoff's law of radiation, a good absorber is also a good emitter. Therefore, when placed in a cold chamber, the charcoal will radiate and lose heat more rapidly than the steel.
Although the charcoal is at a higher temperature, steel has a significantly higher thermal conductivity. When touched with bare hands, heat transfers from the steel to the skin at a much faster rate than from the charcoal, causing the steel to feel hotter.