The wires leading to and from a 0.12 mm diameter lightbulb filament are 1.5 mm in diameter. The wire to the filament carries a current with a current density 4.5 X 105 A/m2. What are (a) current and the (b) current density in the filament

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?