During a classroom demonstration, the instructor clumsily fails in an attempt to push a 2.001 cm diameter brass sphere through a 1.999 cm opening in a steel ring. the instructor then heats the steel ring until the sphere “just” slips through the opening. if the initial temperature of the ring is 20.0 oc, calculate the minimum temperature of the ring at which the sphere slips through the hole. note that the coefficient of linear expansion of steel is 12x10-6 oc-1

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

it is b. absorbs thermal energy