Why are not 1700 , 1800 and 1900 leap years but is 2000 ?

Like we said in the previous question that every year is divisible by 4 is a leap year.But 1700 , 1800 and 1900 are divisible by 4 and not leap years. because of the earth needs exactly 365.242199 days not 365.25 to

orbit the sun.So,a year is a leap year if it is not only divisible by 4 but also by 400.

Why compass needle always points North ?

The Earth has its own magnetic field , it acts like there is huge bar magnet buried inside,but this bar magnet is not on the earth rotational axis it is shifted by some angle.The south of the bar magnet is on the magnetic north and the south polarity is on the magnetic north(image).As opposite polarities attract the magnetic needle (north) is attracted to the south polarity in the magnetic north.That’s why the needle always points north.If you want to know “why earth has magnetic field?”go to letter E.

Why Roads Are Black in Colour ?

There are reasons for why roads are black in colour that I identified and I want to share with you :- Asphalt concrete is available at a low price. The cost that occurs to made of asphalt roads is also low. During the summer and high temperatures, the black color does not reflect the solar waves that will help us to see the roads clearly. Asphalt concrete absorbs heat but that doesn’t affect visibility in extremely hot conditions. In night times bright colors can be easily seen on black roads. whereas bright colors on white roads cannot easily be identified. We can easily say that white lines can be easily identified on black roads whereas white line road markings cannot be identified easily on the white roads. In addition, any irregularity on the road, with the exception of the black color, can be simply detected.

Why does magnet attract some metals ?

Metals are conductors of electricity,and as known conductors have free electrons.Each electron acts as a bar magnet and it has a north and a south pole.When we put the metal next to magnet,the tiny magnets(free electrons)all line up in a certain way that they are attracted to the magnet.For example,if I approach the south pole of a magnet to a piece of iron,the tiny magnets(free electrons) in the iron piece will line up where all the north poles face the south pole of my magnet.And unlike polarities attract. Something to know:If you want to know why electrons behave like tiny magnets you might ask why they are charged in the first place .Actually no one knows!.

Physistri

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