Why should the solvent be near the top of the filter paper at the end of chromatography

An electric current in a wire will push or pull on a permanent magnet. which statement best explains how an electric current creates an electromagnetic force on another magnet?

Mutt and jeff are running along a path each pushing a cart loaded with rocks. if mutt's wagon has a mass two times greater than jeff's and they want to stay together, arriving at their destination at the same time, what must happen? a) jeff should slow down so mutt can catch up. b) mutt must use half as much force to push his cart. c) mutt must use twice as much force to push his cart. d) mutt and jeff will use the same force, but mutt will take bigger steps.

Under normal conditions, describe how increasing the temperatures effects the solubility of a typical salt