  We consider electrons in uniform external magnetic and electric fields which
move on a plane whose coordinates are noncommuting. Spectrum and eigenfunctions
of the related Hamiltonian are obtained. We derive the electric current whose
expectation value gives the Hall effect in terms of an effective magnetic
field. We present a receipt to find the action which can be utilized in path
integrals for noncommuting coordinates. In terms of this action we calculate
the related Aharonov--Bohm phase and show that it also yields the same
effective magnetic field. When magnetic field is strong enough this phase
becomes independent of magnetic field. Measurement of it may give some hints on
spatial noncommutativity. The noncommutativity parameter \theta can be tuned
such that electrons moving in noncommutative coordinates are interpreted as
either leading to the fractional quantum Hall effect or composite fermions in
the usual coordinates.
