A toaster has a heating element which has a temperature coefficient of resistivity of 2.0 x 10-3 (°C)-1.The toaster is plugged into an outlet which delivers a constant voltage. If the resistance of the wire did not change with temperature, the toaster would be able to toast a piece of bread (at 22 °C) in 20 s. If the toaster reaches a temperature of 250 °C, how long does it actually take to toast the same piece of bread?

Si cantilever metal layer polySi heater Figure 2: Top view of the thermal bimorph cantilever structure showing the cantilever, metal layer, and poly§i heater layers in no particular order

A scientist working under emergency conditions at a jungle based lab realizes that her primitive radio has shorted in the rain and burned out a resister. She wants to match the original resister of 2.50 Ohms but believes that a resistance between 2.25 - 2.75 Ohms would be sufficient. All she has to work with is a spool of fine lead soldering wire and some scrap equipment. a) The wire has a diameter of 1.5 mm and the resistivity of lead is 22*10-8Ohm-meters. How much lead wire would she need to make the resister? b). Looking around the lab she is able to scavenge two 3.5 ohm and one 1.0 ohm resisters from old equipment. Using these three resisters how close can she come to building a 2.50 ohm resister? Explain the optimal configuration and calculate the equivalent resistance.