Recent content by goodphy

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    Ratio of the Electric field to the Magnetic field

    Dear all. I would like to know the general expression of the ratio of the electric field strength E to the magnetic flux density B. I know E/B = c, where c is the speed of light, for a vacuum, but I want to know if this is stil valid for any material where the electric and magnetic fields are...
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    How a TFP (Thin Flim Polarizer) works?

    Hello. I've been really curious about how TFP (Thin Flim Polarizer) works. I've searched TFP information through the Internet which tells that TFP utilizes Brewster's angle. This explains how the P-polarization transmits TFP with 100 % transmission, but I don't know how the S-polarization is...
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    I What is the origin of Van der Waals force?

    Hello. Thank you for giving me the explanation. I thought the electron cloud fluctuation occurs even at completely isolated ground state neutral atom. However, you said such a fluctuation occurs only when there is external interaction with it. So, for the isolated atom in the ground state, the...
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    I What is the origin of Van der Waals force?

    Hello. What I know about the Van der Waals force is that it comes from an instantaneous electronic cloud flucutation of the netural atom. This instantaneous electric dipole of the atom attracts electrons in nearby neutral atoms so other electric dipoles are induced on those atoms. As a result...
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    I Is a quasi-static but irreversible process possible?

    Thanks you! you and Chestermiller suggest examples of a quasi-static and irreversible process. I've searched the internet and found that the reversible process is quasi-static but its converse is not guaranteed. So, I think the definition of the reversible process given in my book has some hole...
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    I Is a quasi-static but irreversible process possible?

    Hello. I read the textbook of the thermodynamic and it said the definition of the reversible process as "thermodynamic process which is slow enough so the system state is always infinitesimally close to the thermodynamic equilibrium (quasi-static) during the process. Such a process can always...
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    In 3rd step of Carnot cycle, work done on the piston is pdV?

    Hm...I got some idea right now. The force –Fpg may not be taken into account in a calculation of the work done on the piston since the origin of this force is the piston itself; the work with –Fpg on the piston may be the work done by the piston itself via the reaction force. It is reminiscent...
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    In 3rd step of Carnot cycle, work done on the piston is pdV?

    Hello. I really don't want you to be bothered; But..why is -Fpg same to Fpres ? I think they're different entities. Fpres is from the collisions of gas particles on the piston bottom wall, while Fpg is from the state that the piston is pushing the gas downward. Their origins are different, so...
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    In 3rd step of Carnot cycle, work done on the piston is pdV?

    I appreciate your kind comment:) I would like to simply accept your force balancing on the pistol; your drawing really fits what the thermodynamic textbook try to explain. However, I'm still in trouble. Let's have an extension of your drawing. Here, there is another force on the pistol from...
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    Why is entropy a state variable even for irreversible path?

    Hello. The entropy S is a state variable or state function as the integral of dS = dQ/T is a path-independent, provided that the path is reversible process path. However, such a path-independency of the integral breaks down when the path includes irreversible process. So, I guess we can only...
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    In 3rd step of Carnot cycle, work done on the piston is pdV?

    I see. I think I finally got the right answer. Thanks for all of you to guide me along a right track! I attached the summary of what I've learned from your answers and I hope this would helpful for other guys who have similar question.
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    In 3rd step of Carnot cycle, work done on the piston is pdV?

    Hello. I think you suggested me a way to break through my confusion. Yes, the piston is receiving forces from two things simultaneously; one is the external agency pushing the piston by the force Fe, and another one is the gas pushing the piston due to Newton's 3rd law Fgp (external agency...
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    In 3rd step of Carnot cycle, work done on the piston is pdV?

    Hello. First, look at the figure describing Carnot's cycle. In 1st step (A → B) and 2nd step (B → C), I fully understand that the work done on the pistol (surrounding) by the gas (system) is dW = pdV where dV = Adl since F = pA is the only force on the pistol from the gas (I assumed there...
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    Can a time-varying magnetic field pass a metal sheet?

    Hello. I'm sorry but I don't understand your geometry. The circumferential magnetic field around the conductor will induce a voltage on another wire which is in parallel oto the first conductor? This EMF is very different than what I'm used to such as a solenoid coil so I don't get how EMF is...
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    Can a time-varying magnetic field pass a metal sheet?

    Hello. I'm using CT (Current Transformer) to measure the current flowing on the power line. The frequency of the current is 13.56 MHz. CT appeared to be metal-shielded (This metal case of CT may be grounded when CT is used). CT has a toroidal shape and the power line under the measurement...
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