Discussion
Hot water is poured simultaneously into four metallic tumblers painted outside with different paints. After some time the water will be found to have cooled most in the tumbler painted
Answer: B
The water cools most in the tumbler painted rough black.
Kirchhoff's law says a good absorber is a good emitter, and a rough black surface has emissivity near 1, so it radiates fastest. By the Stefan-Boltzmann law the rate is \(E = e\sigma A T^4\), and roughness raises the effective area as well.
No comment is present. Be the first to comment.
Loading…
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development