A 3/16 in. thick acrylic testing box with dimensions of 10 in. x 10 in. is covered with an unknown ½ in. insulation material. Determine the thermal conductivity for the insulating material if a 25W bulb is used to heat the box. The bulb maintains the inside temperature at 10ºC higher than the outside temperature. Convert all units to metric but do not include units in the answer field.

Awall of 0.5m thickness is to be constructed from a material which has average thermal conductivity of 1.4 w/mk. the wall is to be insulated with a material having an average thermal conductivity of 0.35 w/mk so that heat loss per square meter shall not exceed 1450 w. assume inner wall surface temperature of 1200°c and outer surface temperature of the insulation to be 15°c. calculate the thickness of insulation required.