Questions 2-6

2. We wires have the same length and cross-sectional area. One is copper and the other, gold. Which will have more resistance to current? Which metal listed in your Reference Tables would have the least resistance? Why did the Manhattan Project people borrow silver from the Treasury Department? Why is gold used in cable connections? 3. Find the resistance of an aluminum wire that is 6.0 meters in length and has a crosssectional area of 3.5 x 10'6 m2. 4. A 1.3 m long wire with a crosssectional area of 7.9 X 10'7 m2 is found to have a resistance of 2.8 x 10'2 Q. What material is the wire most likely made from? 5. One factor that is not in the equation R = pL/A is temperature. But R does actually depend on temperature because any changes in temperature will cause the resistivity p to change, which then affects R ' When current ows in a conductor, the electrons run into the metal's atoms. These collisions generate 3; heat and raise the temperature of the metal. When the temperature increases, the atoms of the metal vibrate faster. This makes it more difcult for electrons to nd their way through the metal. How will this affect the resistance of the metal? A superconductor is a material that behaves like a normal metal except when very cold temperatures are ' 'a'eached. At a certain temperature, the resi , a superconductor drops to zero. The resistance of a semiconducto' \" ' "' ' beryllium actually decreases with increasing temperatures. The reason is that when a d extra charge carriers are created, so that more - current can ow. More current means 1" ~ '