Let's say you place a metal tray of foam pieces on top of a van de graaff generator. you turn it on and nothing happens right away but in a few seconds the foam pieces begin flying out of the pan. why does this happen?
a. the van de graaff generator produces an anti-gravity current.
b. the foam pieces have a lower density than air once they're charged.
c. the foam pieces acquire the same charge as the round shell of the van de graaff generator.
d. the foam pieces build up an opposing electric field to the van de graaff generator and cancel its effect.

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia