Conductors and Insulators. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them.onductors and Insulators. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them.
Butterhead lettuce. A type of head lettuce whose botanical name is Lactuca sativa var. heirloom. Two common types are Boston and bibb lettuce. Have small, round, loosely formed heads with soft, buttery-textured leaves ranging from pale green on the outer leaves to pale yellow-green on the inner leaves.
Almost any kind of leaf lettuce will grow quickly in a hydroponic system. Some of the types to try include Romaine, bibb and butter crunch, all of which are ready in three to four weeks. Head lettuce, such as iceberg, will grow well, but the heads take about twice as long to be ready as the leafy types. When growing leaf lettuce, harvest just the outer leaves of the plants and leave the inner leaves to grow, to give you a crop you can harvest almost every day.