The ideal ballast often consists of linking pieces that drain well and allow many different types of modifications to be made. Materials that should not be used are those that will create a smooth texture and later block all types of drainage. Pebbles and limestone are very good examples of bad ballasts. However, examples of good ballasts include fragments of granite and sandstone.
Ballast systems consist of the pumps and piping used to fill and empty ballast tanks. (Ballast tanks are filled to improve the trim, or stability, of a ship that is not carrying cargo.) To reduce pollution, past practices of filling empty fuel and cargo tanks with ballast are no longer allowed.
A ballast reactor consists of a coil wound around an iron core and connected with a fluorescent, or vapor lamp. The coil compensates for a negative-resistance characteristic of the lamp by providing an increased voltage drop as the current through the lamp is increased.
Ballast water is water that ships take up to maintain stability during transport; this water usually contains invasive organisms, or organisms that enter an ecosystem where they are not native, usually as the result of human activities. Most of the time, ballast water is the main reason invasive species are introduced to new ecosystems.
A ballast resistor has the characteristic of flowing in resistance as the flowing current rises and falls. As a result, the ballast resistor often keeps a steady current throughout the entire resistor, despite differences in applied voltage or variations to the entire circuit.