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A 1.50-m cylindrical rod of diameter 0.500 cm is connected to a power supply that maintains a constant potential difference of 15.0 V across its ends, while an ammeter measures the current through it. You observe that at room temperature (20.0$^\circ$C) the ammeter reads 18.5 A, while at 92.0$^\circ$C it reads 17.2 A. You can ignore any thermal expansion of the rod. Find (a) the resistivity at 20.0$^\circ$C and (b) the temperature coefficient of resistivity at 20$^\circ$C for the material of the rod.

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A. $1.06 \times 10^{-5} \Omega \cdot \mathrm{m}$B. $\alpha=0.00105\left(\mathrm{C}^{\circ}\right)^{-1}$

Physics 102 Electricity and Magnetism

Chapter 25

Current, Resistance, and Electromotive Force

Section 2

Resistivity

Cornell University

Simon Fraser University

McMaster University

Lectures

09:29

In physics, a current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. The SI unit for measuring a current is the ampere (A), defined as one coulomb of charge per second.

11:26

02:50

A 1.50-m cylindrical rod o…

08:25

A 1.50 -m cylindrical rod …

03:46

A $1.50 \mathrm{~m}$ cylin…

01:21

A 1.50 m cylindrical rod o…

08:06

07:15

A $1.50-\mathrm{m}$ cylind…

05:49

A 1.50-m cylinder of radiu…

02:11

A resistor is constructed …

02:27

A coil of Nichrome wire is…

so in this problem. Uh, so we have the couple wire and the whole lens. It's 1.5 meters and the diamond is Ah ah, 25 centimeters. So, uh, because this problem we know Ah, the tow. The potential difference between insurance V is 15 volts and ah ah. We put this ah, piece of piece of wire into different the temperature and different into ah surroundings in different temperatures. So first wise 20 sells his degrees and the otherwise Ah, 92 so six degrees. So, uh, we'll have different resistive ity in the two surroundings For this one simply run out. And for this one, its rollout one plus our phone times 92 minus 20 which is 72 degrees. So we have this two different Ah, resistive it, ese. So we can have a different ah resistance resistance. But at the two different temperatures. So for this one, it's Ah Rho knocks ale over ass was all over a right. And for this wine, sir, run out one plus 72 our fall times l bray so we can lease the two equations. The first equation is ah ah ah The current 18 0.5 times roll knots out over a this sequel the total potential difference, which is 15. So this just almost long, ray, high times are equal. Be So this is the first equation. And the second equation is ah, we have a different current, which is 17 17.2 Time's run out one plus 72 Arfa El Rey. Yeah. So this is also equal 15. So we have these two equations, right? And in this two questions, the only on the verbal Ah, are someone's that run out And the other ones, these are far So we're gonna resolve this to permit is independently. And we have found that role not equal 1.6 times 10 to the negative number five o meter and our fires Ah, 1.5 times turned to the navy of three, Purcell says Degrees. Okay.

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