The electrical resistance of a wire varies directly as its length and inversely as the square of its diameter. a wire with a length of 200 inches and a diameter of one-quarter of an inch has a resistance of 20 ohms. find the electrical resistance in a 500 inch wire with the same diameter.

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?