Question

why is the value of g maximum at ples and minimum at equator

Answer 1

1 reason is that earth is not a perfect spherecial in shape
2 reason is that there is more centripetal force at poles then equator

Answer 2

the value of g is maximum at poles and minimum at equator because our Earth is not a perfect sphere .our Earth is bulged out at the equator and flattened at the poles