Thermodynamics - 4-4 Ideal Gas Specific Heat example 4

Calculating U (internal energy) and boundary work for the conservation of energy equation.
Ideal Gas. Like and subscribe! And get the notes here:

[chrissmith]

This helped so much with me so much with one of my assignments. Thanks dude great explanation.

[hakanavc]

Hi professor, thank you so much for helpful videos. Process 1-2 is a constant volume, then 2-3 is constant pressure. Why dont we use cp ? Why do we use only cv ? I guess we should use cv for the process1-2 and cp for the process 2-3. If we use boundary work, then we dont need cv. We can directly solve it with table A-17. But we use only cv. I think this problem should be divided into the two parts. Then we can use cv and cp together.

[davidcohen]

Hi Professor, In all other of your videos, you say "expansion" is work out (+) and "compression" is work in (-)... I don't understand why you take Wb as (-) even though it is "expansion" (+).

If you don't mind, would you be able to clarify this confusion?
Thanks in advance😁

[vidhyamakwana]

A well insulated frictionless piston-cylinder assembly contains 0.5 kg of air initially at 75℃ and 300 kPa. An electric-resistance heating element inside the cylinder is energized and causes the air temperature to reach 150 ℃. The pressure of the air is maintainded constant throughout the process. Determine the work for the process and the amount of electrical work.

[Justin-yceb]

How come you used Cv instead of Cp? The piston is moving while the heat is added right, therefore pressure is constant and volume is not. Right?

[qanimfarah]

Hey professor, i would appreciate if you explain
why do we have to calculate T_av to find Cv? what if we use one of the Ts?

[danialraja]

Hi professor, i was stuck on this question and i tried as hard as i could but i cannot do it. Can you provide a solution for this questions please? A piston-cylinder device initially contains air at 250 kPa and 500 0C and total enclosed volume is 400 liters. Due to the heat loss, the piston moves downwards to a position where it sits on a pair of stops and its final enclosed volume is 200 liters. Further heat loss leads to the pressure reduced to 200 kPa

Determine (a) the final temperature, (b) the work done by the air, and (c) the total heat loss to the environment.

Assuming: 1) air is a perfect gas; 2) there is no friction between piston and cylinder walls, and 3) ignore the volume occupied by the stops; 5) there is no air leakage; 4) C_p=1.013 kJ/kgK; C_v=0.726 kJ/kgK; 5) use 273 for the conversion between Celsius and Kelvin degrees.

[mecha_engineer]

Since it's not a constant pressure process.. Shouldnt the boundary work have been delta p times delta v???

[sevgipnar]

ın 10:06 why we take Tavg? the formula is deltaT. why we didnt write T2-T1?

[sannafinsrud]

how can you tell that the pressure is constant from 2-3 ?

[afinanadiyah]

why suddenly Q-140kJ? wasn't the formula is Q+W+Wb=dU?

[syarizahnorhashimah]

u calculated 1400-300 and divide 2 for the average.. which equals to 550.. shouldnt we find Cv at 550K instead?