a) what would be the effect of a change of tempereature on the resisivity?b) what is the resistance of a copper bus bar 10 meters long and 0.3* 0.3cm in cross section?c) calculate the resistance of 40km of No. 22 gauge copper wired) assuming the lab room temperature to be 20 C, Compute the resistivity of copper at 0C
Always cover both when stopping. The most braking ability is provided by the front brake, as more weight shifts to that wheel as the brakes are applied. Some bikes have antilock brakes and some have both antilock and integral (some BMWs). That is the hand brake controls both front and back brakes at the same time.
I use both brakes on the street. Braking in the dirt or on the race track is a completely different game. The only time I use one brake only is usually the rear - when I'm holding the bike on a hill at a stop or when I'm slowing my street bike on sand or dirt at low speeds. The only time I use the front brake only is on a sport bike when the rear wheel comes off the ground - ease up on the rear brake as the rear tire unloads - you don't want to skid the rear tire while braking.
This excerpt is taken out of a book that I'm currently reading. I found this section on Marciano fascinating! Rocky Marciano who trained with the most monastic devotion; his training methods have become legendary. In contrast to reckless fighters like Harry The Human Windmill Greb, who kept in condition by boxing all the time. Marciano was willing to seclude himself from the world, including his wife and family, for as long as three months before a fight. Apart from the grueling physical ordeal of this period and the obsessive preoccupation with diet, and weight, and muscle tone, Marciano concentrated on one thing; the upcoming fight. Every minute of his life was defined in terms of the opening second of the fight. In his training camp the opponent's name was never mentioned in Marciano's hearing, nor was boxing as a subject discussed. In the final month Marciano would not write a letter since a letter related to the outside world. During the last ten days before a fight he would see no mail, take no telephone calls, meet no new acquaintances. During the week before the fight he would not shake hands. Or go for a ride in a car, however brief. No new foods! No dreaming of the morning after the fight! For all that was not the fight had to be excluded from consciousness. When Marciano worked out with a punching bag he saw his opponent before him, when he jogged, he saw this opponent close beside him, no doubt when he slept, he saw his opponent constantly --As the cloistered monk or nun choose by an act of fanatical will to see only God. Madness? -or merely discipline? -this absolute subordination of the self. In any case, for Marciano, it worked.
A) for most materials (excluding semiconductors), resistivity increases by a roughly proportional amount with temperature change. Semiconductors have the opposite trend, which makes them interesting, but not necessarily useful. What make semiconductors as wildly useful as they are is the process of doping. For the rest of the problems, you will be using R rho*L/A and it is up to you to look up copper's resistivity, and the meaning of wire gauge. Caution: be sure to convert L to meters and A to square meters. For d, you will use rho rho_ref*(1 + alpha*(T - Tref)) where ref subscript refers to reference temperature of 20 C and unsubscribed states refer to the temperature of interest (0 C). You will need to look up reference resistivity of copper, along with copper's temperature coefficient of resistivity (alpha) this is standard plug and chug
A) The electrical resistivity of a hydrogenated LaNi5 thin film has been investigated as a function of temperature in vacuum and in hydrogen. While the film was heated in vacuum for the first time, the change in resistivity exhibited different characteristics during different ranges of temperatures due to the competition of two effects owing to the lattice scattering of conductive electrons and the number of them. The resistivity had a sharp drop near 600 K, which originates from the formation of high conducting lanthanum hydride and nickel due to a reaction between the dissolved hydrogen and LaNi5. The change in resistivity was not repeatable during the successive heating and cooling processes. When the film was heated under a hydrogen atmosphere, a drop in resistivity occurred near 700 K due to the reaction between LaNi5 and the hydrogen atmosphere. The film showed a linear temperature dependence of receptivity with completeness of the reaction. It was found that the reaction was irreversible. The film lost the ability of hydrogen absorption after the reaction, and it had a phase change from LaNi5 to LaH and Ni. This result was supported by x-ray diffraction patterns. B)Resistance of a wire in Ω R ρL/A ρ is resistivity of the material in Ω-m L is length in meters A is cross-sectional area in m? A πr?, r is radius of wire in m A π(0.0015)? 7.07e-6 square meter 0.005 (1.69e-8)L / (7.07e-6) L 2.09 meters
