The Millikan oil-drop experim ent, w hich was the first experim ent to measure the charge of the electron, com pared the electrical force on a small charged oil drop with the force exerted on this drop by gravity. T he experim ent thus required a knowledge of the weight of the drop. This weight can be obtained by observing the drop falling with a constant term inal velocity w hen the gravitational force on the drop is balanced b y the frictional force due to the viscosity of the surrounding air. (The air is at atm ospheric pressure so that the mean free path of the air molecules is m uch smaller than the diam eter of the drop.) The term inal velocity with which the oil drop falls is inversely proportional to the viscosity of the air. If the tem perature of the air increases, does the term inal velocity of the drop increase, decrease, or rem ain the sam e?

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