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.
There are five distinct types of lettuce: leaf (also called loose-leaf lettuce), Cos or romaine, crisphead, butterhead and stem (also called asparagus lettuce). Leaf lettuce, the most widely adapted type, produces crisp leaves loosely arranged on the stalk.Nearly every garden has at least a short row of leaf lettuce, making it the most widely planted salad vegetable. Cos or romaine forms an upright, elongated head and is an excellent addition to salads and sandwiches.t is a head lettuce that is also low in nutritional value and flavor. Because of its superior shipping qualities, iceberg has been most available which accounts for it popularity. The most abundant nutrient in iceberg lettuce is water.