Magnet which has the shape of a rectangular prism.

Does heating a metal wire increase or decrease its electrical resistance? why?

Newtons view of arrangement of the universe. don't copy from anywhere.

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?