Question

why most of srilanka has the equatorial type of climate​

Answer 1

There are several factors that influence the amount of sunshine received at various places on the earth. The major factor is that while the sun is overhead at the equator, it is at a rather slant angle at the poles. This effect can be demonstrated using a torch, which can be taken as the sun.

Answer 2

not only Sri Lanka but all southern part of it is having equatorial type that is Tropical Rain forest it is because it lies in between 10 degree north and 5 degree North latitude which is close to equator that is zero degree latitude