  We find two new classes of exact solutions to the Einstein-Maxwell system of
equations. The matter distribution satisfies a linear equation of state
consistent with quark matter. The field equations are integrated by specifying
forms for the measure of anisotropy and a gravitational potential which are
physically reasonable. The first class has a constant potential and is regular
in the stellar interior. It contains the familiar Einstein model as a limiting
case and we can generate finite masses for the star. The second class has a
variable potential and singularity at the centre. A graphical analysis
indicates that the matter variables are well behaved.
