I want to say its cooled by reflection because of the foil, sun reflects off of the foil back into the atmosphere. I don't think it's conduction because I have the foil on my windows and it's never warm to the touch. it's not a liquid so I don't believe it's convection. The foil reflects the radiation so I don't think it's b, c or d. so I wanna say A but I'm not 100% sure
Explanation:
When you observe the night sky you will notice that the stars are moving. They rise from eastern horizon and set in the western horizon. It happens due to rotation of Earth. When observed closely you will notice that the all the stars seem to go around the pole star. Out of all the stars there are some stars which neither set not rise, such stars are called as Circumpolar stars. This means that they are always above the horizon. If we trace the path of such stars they will appear to make complete circle around the pole star.
Also, you will notice that the altitude of pole star (separation of pole star from the horizon in degrees) will depend on the location of observe on the Earth. This happens due to Earth being spherical. So if you are on equator the pole star will be on the horizon i.e. 0° altitude. If you are at Poles, altitude of the pole star will be 90°. Technically the altitude of pole star at any place on Earth is equal to the latitude of the place.
If the altitude of pole star varies and increases as you move towards higher latitude on Earth, the distance between horizon and pole star will also increase. This will result in more stars being circumpolar.
If you are at Poles, all the stars will be circumpolar and if you are at equator no star will be circumpolar.
It depends on Mass and velocity
17. a
18. c
19. a
20. c
21. c
Answer:
The value is 
Explanation:
From the question we are told that
The length of the solenoid is 
The radius is 
The number of turns is 
The current it carries is 
Generally the magnitude of the magnetic field is mathematically represented as
Here 
is the permeability of free space with value 
=> 
=>
