Which of these materials is an insulator?

Plastic, rubber, wood, and ceramics are good insulators. These are often used to make kitchen utensils, such as saucepan handles, to stop heat from flowing up to burn the cook's hand. Plastic coating is also used to cover most electrical wires in appliances. Air is also a good insulator of heat.

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it