A star is the body of gas in which nuclear fusion of gases like helium and hydrogen takes place due to this reason the star glows or dim. Star gets the ability to generate light because of this nuclear fusion which cannot be observed in planets although the process of generation of star and planet is the same. In distantly located star under observation, it's luminosity ( the property of emitting lighting) is controlled by size of the star, the larger the size of the star it will have greater surface area the more profound will be the nuclear fusion in it and more light will be emitted. Second factor is the gaseous interaction of gases in and around the star and their temperature which causes the change in the light which has to pass through a layer of these gases. Therefore, the distant star observed will show light fluctuations.
Kirchhoff’s junction law states that the sum of current(mass charge) flowing in and out of the junction must be equal to zero. This law emphasizes conservation of charge and energy. Charge is also a form of energy and it can neither be created nor destroyed.
If a pulley system has an efficiency of 74.2%, then only that fraction of the work performed will be useful. 74.2%=0.742. 0.742*200 is about 148J. Hope this helps!
