Water on a smooth floor can made you slip, which means water is also a lubricant. can you think of reasons why oil and grease and not water is used i machines as a lubricant?

The boiling of water is 100°, while the boiling point of lubricating oil is anywhere from 370°-600°. So oil is used because if the machine gets too hot, then the water may boil off, which will make the machine lose its lubrication.

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