A Van de Graaff generator is used to build up charges on the outside of a sphere. A belt is charged with electrons by rubbing
against a rough pulley. These electrons are then transferred to a metal sphere and spread out even on its outer surface. When
objects are brought near the sphere, they are either attracted or repelled by the sphere even if they do not touch.
If a charged object is brought near the sphere, how is the charge on the sphere related to its motion?
Any charge will be attracted to the sphere.
A negative charge will be repelled by the sphere.
A positive charge will be repelled by the sphere.
D)
A negative charge will be attracted to the sphere.

b.transmitters send radio waves, and receivers capture radio waves.

multiply 2kg by latent heat of vap

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