(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A resistance, connected to a battery, is put inside a thermally insulated cylinder which has an adjusted frictionless piston and contains an ideal gas. Through the resistance, a current i = 240 mA flows. At which velocity v should the piston move upwards, so that the temperature of the gas remains constant? The value of the resistance is R = 550 ohms and the mass of the piston is 11.8 kg.

[Note: the attached picture is scanned from "Physics" by Halliday, Resnick and Krane, 4th edition, Brazillian Portuguese version.]

2. Relevant equations

Joule effect:

[tex]P=Ri^2[/tex]

3. The attempt at a solution

[tex]P=Ri^2 = (550)(240\times 10^{-3}) = 132 W[/tex]

So, if this energy is entirely transferred to the gas, then the gas receives 132 J at each second.

If the volume remained constant, the temperature of the gas would increase. So, the piston should move upwards, thus allowing the gas to expand, increasing its volume and keeping the temperature constant.

I'm not sure if I understand this situation properly. I think that the heat Q transferred to the gas at each second equals 132 J. This heat will equal the work done by the gas against the piston to expand, maintaining the temperature constant.

I'm not sure how to proceed from here. I also don't know how the weight of the piston will interfere in the process.

Thank you in advance.

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# Homework Help: Question involving resistance and heat transfer

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